PTYCHOPTERA PALUDOSALIMNOBIA REPLICATA

From enlarged photographs, made at the Yorkshire College, Leeds, from specimens bred by the Author, and mounted by Messrs. Watson & Son, High Holborn, London

THROUGH
A POCKET LENS

BY

HENRY SCHERREN, F.Z.S.

AUTHOR OF
‘PONDS AND ROCK POOLS,’ ‘A POPULAR HISTORY OF ANIMALS,’ ETC.

WITH NINETY ILLUSTRATIONS

THE RELIGIOUS TRACT SOCIETY

56 PATERNOSTER ROW AND 65 ST. PAUL’S CHURCHYARD

1897

Oxford

HORACE HART, PRINTER TO THE UNIVERSITY

CONTENTS

LIST OF ILLUSTRATIONS

THROUGH A POCKET LENS

CHAPTER I
THE POCKET LENS, THE DISSECTING MICROSCOPE, AND SOME SIMPLE APPLIANCES

The object of this little book is to show how much may be seen with an ordinary pocket lens, and with a simple microscope; and, as far as possible, to dispel the idea, far too common, especially among beginners, that no real work can be done unless one has a compound microscope, with a large battery of lenses and an array of ‘accessories.’

It would be easy to multiply quotations, from high authorities, in support of the proposition implied in the foregoing paragraph. Two only must suffice.

In a recent review of a very good book dealing with Butterflies and Moths (Natural Science, vol. vi. p. 293), the following passage occurs: ‘The only suggestion we should like to make is that a compound microscope is unnecessary for any of the details that the author mentions. A first-rate platyscopic hand lens is much more convenient and the young naturalist should train himself thoroughly in the use of it. There is no more common error than the undue use of the higher powers of a microscope. Except for the intimate details of histology, a low power or a hand lens is much more easy to use, and its employment gives a much better idea of the structure.’

The next quotation is of greater interest, as it gives some insight into the way in which Darwin carried on his investigations. In the Life and Letters of Charles Darwin (vol. i. pp. 145, 146) we are told: ‘His natural tendency was to use simple methods and few instruments. The use of the compound microscope has much increased since his youth, and this at the expense of the simple one. It strikes us nowadays as extraordinary that he should have had no compound microscope when he went his Beagle voyage; but in this he followed the advice of Robert Brown, who was an authority in such matters. He always had a great liking for the simple microscope, and maintained that nowadays it was too much neglected, and that one ought always to see as much as possible with the simple before taking to the compound microscope. In one of his letters he speaks on this point, and remarks that he always suspects the work of a man who never uses the simple microscope.’

It may be well here to verify the quotations, and also to consult Darwin’s Naturalist’s Voyage, to ascertain what kind of objects he examined with the simple appliances at his command. In the first chapter there is an interesting account of a curious limy deposit on the rocks of the island of St. Paul’s, and of the discoloration by confervae of the water, which, ‘under a weak lens, seemed as if covered by chopped bits of hay, with their ends jagged.’ Then we have an account of the confervae in the Indian Ocean, and of infusoria so numerous as to tinge the water off the coast of Chile. In the second chapter we have observations and experiments on planarian worms. ‘Having cut one of them transversely into two nearly equal parts, in the course of a fortnight both had the shape of perfect animals.’ In the next chapter he records some observations on the structure of vitrified tubes formed by lightning striking loose sand. In the fifth chapter is an elaborate description of a kind of sea-pen; and in the ninth chapter there are some remarks on the vast number of eggs in the egg-ribbon of a sea-slug, and on the ‘bird’s-head’ organs in certain Polyzoa. These remarks were, of course, founded on actual inspection with the simple microscope.

To this instrument, also, we owe the discovery of the tadpole-like larvae of Ascidians, or Tunicates, as they are now generally called. ‘At the Falkland Islands I had the satisfaction of seeing, in April, 1833, and therefore some years before any other naturalist, the locomotive larvae of a compound ascidian.... The tail was about five times as long as the oblong head, and terminated in a very fine filament. It was, as sketched by me under a simple microscope, plainly divided by transverse opaque partitions, which I presume represent the great cells figured by Kovalevsky. At an early stage of development the tail was closely coiled round the head of the larva[1].’

We come now to our pocket lens, which may be purchased for a few shillings of any optician. One can buy a serviceable single lens, in an ebonite handle, for a shilling; and this cheap instrument is sufficiently powerful not only to give the worker a good general idea of the form and structure of objects, but to enable him to do real work. With it the habits of many of the inmates of his aquaria may conveniently be watched; he may see their development from stage to stage of their life-history; and with it, when they are broken up, he may make out a good deal of their external and internal anatomy.

Fig. 1.—Hand Magnifier and Stand.

A very good form is shown at Fig. 1, which represents a hand magnifier, fitted with three lenses of different focus, generally 2 in., 1½ in., and 1 in. Examination of the catalogues of the principal London opticians shows that such a set of lenses may be bought for about 3s. In shape and construction there is sometimes a little variation; but the form figured is that most generally adopted, and is, on the whole, fairly convenient. It would, however, be an advantage if the hole by which the magnifier is mounted on the stand were drilled in the solid part of the handle. This would not only do away with the objection that the hole in the case permits dust to penetrate to the glasses, when carried in the pocket, but would give a longer reach, and thus obviate the necessity for moving the stand if the observer were examining a large object. The price of the stand figured is 2s. 6d.; and one with a short adjusting arm ought not to cost much more.

Any one with a mechanical turn may make a stand for himself, though it may be doubted whether this is quite worth while when these articles may be bought so cheaply. Nevertheless, there is great pleasure in making things for oneself; and a home-made stand will enable the observer to do quite as good work as one that came from the optician’s shop.

A bill-file weighted at the foot may be bought for a few pence, and adapted to the purpose. For the slider a large cork cleanly pierced will answer admirably. This should carry a piece of stout wire, bent at the end thus __

, to serve as a holder for the magnifier, which should have a hole in the handle, for the reasons stated above. The only difficulty will be the attachment of the wire to the cork. The Rev. J. G. Wood advocated winding the wire round the cork in a spiral; and this is a very good plan. An increase of steadiness is secured, if a larger cork, or small bung, be used, and the wire inserted in the side.

There are, of course, more expensive lenses, with which better definition can be obtained. Zeiss has an excellent magnifier consisting of two lenses, for use in the dissecting microscope (Fig. 2), and also as a hand lens, at the price of 6s.; one of the same construction, for use in the dissecting microscope alone, may be had for 4s. The Steinheil achromatic lenses are probably the best of all. These are made in powers ranging from 2 in. to ½ in. focus[2]; and the price varies from 10s. up to £1, according to the maker. Those made by Leitz of Wetzlar cannot be surpassed; and they are sold in London at 10s. each, either mounted in a handle, for use as hand magnifiers, or with a collar for use in Leitz’s dissecting microscope (Fig. 3). Mr. Lewis Wright says that ‘the best plan is to combine both uses, and have two or three powers in collars, with a spring ring folding into a handle, which will carry any one of them in that manner. A Steinheil lens at this low price costs little more than a Coddington, while its performance is infinitely superior[3].’ It is a difficult thing to get makers to deviate from the beaten track, and so far as I have been able to learn, Mr. Wright’s wishes have not been fulfilled.

Fig. 2.—Zeiss’s Dissecting Microscope.

The lenses and stand (Fig. 1) constitute a simple form of dissecting microscope. If the worker wishes for something more elaborate, he need only consult the catalogues of the principal makers to find something that will meet his requirements. Zeiss’s brass stand, with stage, above which a lens slides up and down in a holder (Fig. 2), is sold for 9s.; with blocks for supporting the hands, at 10s. It is a useful instrument for small objects.

My favourite instrument is shown at Fig. 3. Here the focussing of the lens is effected by rack and pinion work, by means of the screws on each side the upright pillar. The lens is shown fitted in the collar which carries it. The stage is of glass—roughly, 2½ in. long by 2 in. wide, and the arm at the top of the pillar can be moved from side to side, so as to bring a fairly large object within range. The metal framework of the stage is furnished with nickelled clips (not shown), which serve to hold an excavated slip. The arm-rests are detachable, and the uprights are hinged for convenience of packing. The instrument (with the exception of these rests) packs into a neat, strong mahogany box, 7½ in. in length, and about 5 in. in height and width. With two powers—1 in. and ½ in. are very serviceable ones—the cost is 38s.

Fig. 3.—Leitz’s Dissecting Microscope.

It is to be wished that the maker would devise some plan by which the admirable lenses sold with this instrument could be utilized for the pocket. Mr. C. Curties, of Baker & Co., High Holborn, has kindly done something in the matter, and has made for me a metal holder. I have found this convenient, but should be glad to see something further done in the same direction, so that instrument, lenses, and holder could be sold for £2. This ought to be within the range of practical optics. The spring collar advocated by my friend Mr. Wright seems better, and would certainly be cheaper. The lenses would only need to be dropped in. To use my pocket holder one must unscrew the metal collar from the lenses before screwing them into the metal plates which carry them (Fig. 4). It is, however, something to have made a beginning: it is a step in the right direction.

Fig. 4.—Two Leitz Lenses in holder (open).

Fig. 5.—Two Leitz Lenses in holder (closed).

A serviceable dissecting microscope—not a toy, but an instrument with which real work may be done—can be made at a cost of a few shillings. Such a one has been made for me by a friend with a positive genius for such work. The body is fashioned out of a parcel-post box 7 in. long, 3½ in. in height, and the same in width. From the centre of the sliding top a piece is cut away, leaving ledges to take a 3 in. by 1 in. excavated slip for small dissections, or a mounted slide of a large object, such as a whole insect, for examination. A further portion is cut away on each side to take a small dissecting dish (Fig. 6). To admit the light, a hole is cut in the side of the box; and the mirror consists of a piece of silvered glass which was bought of a hawker in the street. This is placed in the box opposite the square hole, and sloped at an angle of 45°. The aid of a skilled mechanic was sought for a small rod carrying a thread, which works in a piece of brass bent at a right angle. This piece of brass is screwed on the box, just above the aperture by which light is admitted, and carries a pocket magnifier, similar to that shown at Fig. 1.

Fig. 6.—Home-made Dissecting Microscope.

This modest little instrument generally stands on my work-table, and has provoked some remark and a little good-natured banter from friends who have seen it. Nevertheless, I should be sorry to part with it, for I have found it extremely serviceable in many ways. And more than one critic has had to confess that better results were obtained than one would expect from its appearance. The total cost out of pocket was, 3d. for the box, 3s. for the lens, and 1d. for the plate-glass, while the man who made the pillar and ear-piece would take no more than 6d. for his work. This brings the total to 3s. 10d. With a little ingenuity the pillar might be made to carry a collar, and so take a Steinheil lens. This would swell the total cost to about 11s.

Other apparatus need not be costly. An incident occurred at the meeting of the Quekett Microscopical Club on November 22, 1878, which shows how readily common objects may be utilized for our purpose. The late Right Hon. T. H. Huxley, who was at that time President, exhibited, and made some remarks on, the dissecting microscope which now bears his name. During the discussion which followed, Professor Charles Stewart exhibited some little saucers, which were admirably adapted for dissecting purposes. The President said that he should ‘be glad to know where these convenient little saucers could be obtained.’ The next paragraph of the minutes is interesting and instructive. ‘Mr. Stewart said they were to be found at the corners of the streets, containing three whelks or three mussels for a penny. He bought those he had brought to the meeting at a shop in the New Cut, where they were supplied to costermongers[4].’

As very many of the objects with which we are concerned are aquatic, we shall want vessels of some sort to serve as aquaria. Any glass vessel will answer our purpose, provided it is clear, to allow of the examination of our captives; or shallow pie-dishes may be utilized. The glass pots in which preserves are sold will do admirably, and any glazier will cut us covers for a few pence. Within reasonable limits, the smaller the aquaria are the better. The inmates can be seen more easily, and picked out with less trouble when one wishes to examine them.

The principles on which aquaria should be kept are now pretty generally understood. There should always be a small quantity of growing aquatic vegetation, and a supply of minute life to furnish food for the larger forms. Excess of light should be avoided, and the temperature should not be allowed to rise much above 50° F. Carnivorous beetles and their larvae may be fed with small pieces of meat, small garden worms, or tadpoles. Most of the smaller larvae treated of will be satisfied with vegetarian diet, varied with an occasional meal of water-fleas.

Fig. 7.—Beakers.

Fig. 8.—Glass Capsule.

If one cannot lay the household stores under contribution for jam-pots, tumblers, and bottles, beakers (Fig. 7) make capital small aquaria. They are sold in nests, and may be had either rimmed or lipped—rimmed for choice. There is no difficulty in obtaining them of any optician or glass-merchant. Mine have been bought from Messrs. Beck, of Cornhill, as have the capsules, &c., figured here.

Glass capsules (Fig. 8) are made in different sizes, ranging from 1½ in. to 3 in. in diameter, with a height of 1 in. or 2 in. The largest size, 3 in. by 2 in., costs 5d., and a glass circle to cover it, 1d. These capsules will be found useful for small aquaria, and for isolating aquatic larvae in order to keep them under observation during their change to perfect insects. It was in a capsule of this kind that some of my Ptychoptera larvae (p. 184) were kept, and changed into the pupal condition.

The glass block, with cover (Fig. 9), is convenient for a number of purposes. In it small creatures may be examined in air or in water, and it makes an exceedingly convenient little dissecting dish for use with the mounted hand magnifier (Fig. 1), or with Leitz’s stand (Fig. 3), or the home-made stand (Fig. 6). The glass box, with cover (Fig. 10), is extremely good for keeping small creatures under observation.

Fig. 9.—Glass Block, with cover.

Fig. 10.—Glass Box, with cover.

Excavated glass slips, 3 in. by 1 in., may be bought from any optician. They serve for the examination of objects in water, and also for dissection. The best I have been able to get have been supplied by Mr. J. Hornell, of the Biological Laboratory, Jersey, and they are very cheap.

We shall need some forceps to pick up specimens from the vessels in which they are kept, and the same little instruments will be found convenient in collecting. Both forms have advantages of their own; if we are limited to one pair, they should be curved, and of brass. Forceps with ivory tips are very useful for handling aquatic vegetation. These articles are not usually sold by opticians, but are kept by the tradesmen in Clerkenwell who sell jewellers’ and watchmakers’ tools, and cost from 1s. to 1s. 6d. a pair.

Fig. 11.—Forceps.

Dipping-tubes are used to take up small aquatic animals from the vessels in which they are kept. Very little practice will render the use of this instrument easy. The tube is held firmly between the thumb and the third and fourth fingers of either hand, while the index finger is pressed firmly on the top. Most people naturally prefer the right hand, but it is well to accustom oneself to use the right or left indifferently. The open end is then put into the water, just over the object to be secured, and the index finger lifted. The rush of water into the tube will carry the object into it, and if the finger be again applied to the top, the pressure of the atmosphere will prevent the water from escaping when the tube is lifted out[5].

Small brushes are useful for taking up specimens from the water or from pickle; common ones will do very well for large objects, but for small objects and parts it is advisable to have one or two sable brushes, as these form a better point.

Some needles fixed in handles will also be necessary. These may be bought, or made by fixing ordinary needles of requisite sizes into the handles sold for small brushes. The needles must be kept free from rust, and should always be carefully wiped after use. A good plan to keep them clean is to stick them in a gallipot in which has been melted a mixture of lard and paraffin in equal proportions.

Small dissecting-knives are useful, but all the work described here may be done with an ordinary pocket-knife in good trim.

Fig. 12.—Three forms of Dipping-tube. Method of using it.

The best preservative for our purpose is formalin, which is sold in a forty per cent. solution. This should be treated as absolute, and a five per cent. solution made. This will really be a two per cent. solution, and is sufficiently strong for general use.

The most profitable use we can make of specimens is to watch their habits while living, and to break them up and learn as much as we can about their structure when they are dead. For us to make a collection of specimens in tubes would be a waste of material.

Fig. 13.—Mounted Needles.

Little need be said about collecting. The objects treated of are so plentiful that no great skill, nor any wealth of appliances, is needed to secure an ample supply. The following remarks on the methods employed at the Illinois State Laboratory for the capture of aquatic insects and larvae are, however, worth quoting:—

‘Insects in vegetation, and on or in the bottom, were taken by means of a dip-net—a net of about equal depth and width attached to a strong semicircular ring, firmly fixed to a long handle, the straight side of the ring being opposite the point of attachment. For the larger and more active forms, a coarser net was used, and for smaller forms one made of finer net proved most durable and satisfactory. To collect from the mud of the bottom, the water immediately over it was violently stirred and then swept with the net. The surface layer of mud was also scooped up in the fine dip-net, and then allowed to wash through, leaving the coarser contents in the net. Insects on the bottom in deep water were secured by using a dredge, and washing its contents through net sieves. The aquatic vegetation, when free from mud, was violently washed in a large pan, many smaller forms being thus dislodged and coming to the surface. Insects occurring in open water were taken in drawing an ordinary towing-net[6].’

Here we have, so to speak, the general principles of collecting. It will be easy to adapt them to particular cases.

In choosing the subjects to be treated of in this little book, some difficulty has been experienced in deciding what to select from the multitude that lay ready to hand. It was felt necessary that the subjects should be connected, since choosing them at random would lead to purposeless work, and so to waste of time and opportunity. After some consideration, the author has decided to take all the examples from the Arthrop´oda—that great sub-kingdom of backboneless animals which includes the Lobster, the Crab, the Sand-hopper and the Woodlouse, the Spider and the Mite, the whole world of Insects and the Centipedes. One cogent reason that influenced this decision was the fact that these objects are exceedingly common, so that there can be no difficulty in procuring material on which to work. There is, perhaps, no other sub-kingdom so full of interest, on account of the many widely different forms, which may be referred to one common plan.

It may possibly appear to some readers that the powers of the pocket lens have been exaggerated. As a matter of fact the material for the book has been gathered by actual observation. The author has seen, with an ordinary pocket lens, the objects here described. If some are shown as they would appear under greater magnification than such a lens would give, this is chiefly for the sake of emphasizing points of interest which might otherwise be overlooked, but which can readily be made out with a hand magnifier, when attention has been drawn to them, and the observer knows what to look for.

CHAPTER II
ARTHROPODS AND THEIR CLASSES.—THE MARGINED WATER BEETLE; THE GREAT WATER BEETLE; THE COCKTAIL BEETLE

Having got together our apparatus, which, as we have seen, need be neither costly nor complicated, the next step will be to acquire some knowledge of the group from which the examples here treated of will be taken—the Ar´thropods, or animals with hollow-jointed limbs. These are the ‘Insects’ of the Linnaean classification, and, for the matter of that, of popular phraseology; for though few people would now venture to call a Lobster an ‘insect,’ we still style some of its near relatives Water ‘Fleas,’ as Swammerdam did two hundred years ago.

The Arthropods form a phylum, or main division of the Animal Kingdom. Above this phylum comes that of the Molluscs, or soft-bodied animals, such as the Oyster, the Snail, and the Cuttlefish. Still higher are the Lancelet, the Sea-squirts, and some few others, that bridge the chasm between the phyla without, and that phylum with, a backbone. And to this last Man himself belongs.

Two reasons contributed to the selection of the Arthropods as a subject for work with the pocket lens: (1) the great interest which surrounds many of the group; and (2) the ease with which specimens may be procured and kept under observation.

Every one has pretty clear notions as to the general ‘make’ of a Vertebrate or backboned animal. An Invertebrate animal has, of course, no backbone or the semblance of one; the nervecord, where present, lies on the under surface, and forms a ring round the gullet, and the heart lies on the upper surface or back. We may verify this by pulling to pieces a dead insect.

But a phylum, or main division, is much too large to be considered as a whole. It must, therefore, be broken up into smaller groups, which are called Classes, generally reckoned as five in number. These, again, may be grouped into two divisions, according as their members breathe by means of air-tubes (tracheae) or by gills. Our scheme then will stand thus:—

ARTHROPODS		Breathing by air-tubes		Peripatus.
				Centipedes and Millipedes.
				Insects.
				Spiders and their kin.
		Breathing by gills		Lobsters, Crabs, Sand-hoppers, and Woodlice.

This scheme looks well on paper; and on the whole is workable. But among our examples chosen from the Class of Insects, we shall find some that breathe by gills in their larval stage, and by air-tubes when adult. And among the Crabs are some, the gills of which have ceased to perform their normal function, so that these animals cannot live in water for a single day. And then there are the Sand-hoppers and Woodlice.

The body of an Arthropod may be represented by a series of similar rings, thus:

This similarity is clearly apparent in the Centipede, but is concealed in the Beetle, the Shrimp, and the Spider. It seems, at first sight, to be altogether lost in the Crab, and does really vanish in the adult stage of some parasitic Crustaceans.

It may be plausibly objected that our ideal Arthropod resembles nothing so much as a worm. In many respects this is true. A primitive Arthropod was worm-like, as is a Centipede. And Arthropods and Worms were formerly classed together in one group, as Annulo´sa or ringed animals. The chief external difference lies in the nature of the appendages borne by the various rings or segments.

We may represent those of the Worms thus

, for they are bristles, or groups, or modifications of bristles. Those of the Arthropods may be represented thus

, for the appendages are really jointed, though, of course, in a fashion different from those of a backboned animal.

The jointed appendages of Arthropods may be modified to fulfil very different functions. They may serve as legs for walking, hands for climbing or seizing prey, jaws for masticating food, feelers or organs of touch and sense, and, strange as it may seem, in one group, as eyes.

It is well to get some notion of how these joints are formed. To take the body first: the skin connecting the segments is much thinner than that of the segments themselves, which is thickened by the deposition of chitine, and, in some cases, also of carbonate and phosphate of lime. A portion of the body, then, may be represented thus,

where the heavy lines denote the segments, and the thin ones the spaces between the segments. It will be seen that this arrangement allows of considerable play, and also of a telescopic movement by which the segments can be brought close together.

It is easy to construct a kind of model that shall exemplify these movements. Make a tube of calico, some six inches long, and having stuffed it with cotton-wool, paste on it strips of brown paper one inch in width, leaving an interval between each, as in the last diagram. Then we shall be able to understand how Arthropods can bend the body or move it from side to side. And the limb joints are made on a similar plan.

Fig. 14.—Cape Peripatus (natural size).

The most archaic Arthropod—Perip´atus—must be mentioned. It is not found in Britain, nor even in Europe; so that, unless we travel, we shall only know it from books, or from museum specimens. But it is an extremely interesting creature, for it is of worm-like aspect, and breathes by air-tubes, opening all over the body, which has no external segments. The limbs are imperfectly jointed, and each of them bears two claws. Most naturalists make this genus a Class by itself, while some put it with the Centipedes. There are about a dozen species, four of which are African, two Australian, and the rest are found in South America and the West Indies. Besides these there are some doubtful species.

In habit they resemble the Centipedes, and they ensnare the insects on which they feed by ejecting sticky slime from the small processes near the mouth. The left process is shown in the illustration, just below the antenna of that side.

Professor Sedgwick, who described these animals in the Quarterly Journal of Microscopical Science (1888), and, more popularly, in the Cambridge Natural History, says, that ‘the exquisite sensitiveness and changing form of the antennae, the well-rounded plump body, the eyes set like small diamonds on the side of the head, the delicate feet, and, above all, the rich colouring and velvety texture of the skin, all combine to give these animals an aspect of quite exceptional beauty.’

Unfortunately, an illustration in black-and-white can only render form. We must take the beauty of the colouring for granted. One thing, however, cannot escape the most cursory examination of the picture—the resemblance of the creature, in some respects, to a worm, and, in others, to a caterpillar, which, as everybody knows, is the larval stage of a butterfly. If this resemblance sets us thinking how it came about, and what it means, Peripatus will, for the present, have done its work for us.

With these general notions of Arthropods, we may pass on to put our pocket lens to some practical use. Our first subject shall be the Margined Water Beetle (Dytis´cus margina´lis), which can be taken in almost any open pond in the country. Water covered with duckweed should be avoided in hunting for these beetles, which prefer ponds with a clear surface, so that they may easily come to the top to breathe.

Every one has a good general notion of the principal Insect-groups, technically called Orders—Beetles, Cockroaches and Grasshoppers, Butterflies, Bees and Wasps, and Flies. Insects may be defined as animals with hollow-jointed limbs, and divided into three regions—head, thorax, and abdomen. The head bears a pair of antennae; the thorax carries three pairs of legs, and (generally) two pairs of wings; the abdomen is without appendages. Insects when adult breathe by tubes that open to admit air. In Chapter VI we shall see that many larvae obtain an air supply in different ways.

Fig. 15.—Margined Water Beetle (male).

Beetles may be taken as very good types of true Insects. They constitute the Order Coleop´tera, or Insects with sheathed wings, only the hinder pair being used for flight (Fig. 18), and at other times they are folded under the wing-cases, or el´ytra, as in Fig. 15.

We may advantageously compare our Beetle with Peripatus, and note the points of agreement and of difference.

Now, if our captive Beetles are to yield us the greatest possible amount of profit, we shall keep them under observation for some time, so as to watch their habits.

In keeping these Beetles we shall not require a large aquarium. A small gathering of aquatic weed will be necessary to keep the water in good condition and the aquarium ready for its tenants.

My interest in these Beetles was quickened by a letter in the Field (Oct. 28, 1893), in which a correspondent at Weybridge asked ‘for information as to what animal or bird bisects so neatly the shells of the Water Snail (Planorbis).’ I thought then, and know now, that the shells were ‘bisected,’ if that is the proper word, by Water Beetles. From that time I have had, and still have, several living in small aquaria, but for a long time was unable to get direct evidence on the subject.

Fig. 16.—Shells of Molluscs broken up by Dytiscus.

(From a photograph by Cherry Kearton.)

Many experiments were tried, and at last these proved successful. Several specimens of Dytiscus[7] were obtained, and put into a small aquarium in which was no other food for them than some snails and other molluscs. The Beetles were carefully watched, and were several times seen trying the snails. In crawling along the inner surface of the glass, Planorbis and Limnaea both protrude the foot to a considerable extent, and pieces were ripped out by the strong mandibles of the Beetles before the shells were actually broken up.

All the shells represented in Fig. 16 were taken from this aquarium, so that there is good evidence as to what creatures broke them up and devoured their inmates. In these, as in the specimen kindly sent me by Mr. Tegetmeier, the Natural History Editor of the Field, the bisection is not complete, though in all cases it is carried far enough to allow of the extraction of the mollusc. The large Limnaea shell in the centre has been attacked, but it seems to have been left when the beetles discovered it was empty. (The empty shell was noted before the Beetles were put into the tank.) Another Limnaea shell is figured, from which the snail has been picked out, and that of a fresh-water mollusc.

After these observations had been recorded in the Field[8], I found that I had been anticipated by about forty years. I picked up, at a bookstall, a copy of G. B. Sowerby’s Popular History of the Aquarium, and there I found that the author had distinctly seen Dytiscus at this kind of work. He says[9]: ‘I have only once witnessed him in the act of seizing an unfortunate Planorbis or Flat-coiled Water Snail. At first, the Dytiscus seemed to be roaming about in quest of something, first under, then over, the leaves of a water-lily. At last, in a rather dark corner, he seemed to perceive suddenly a Planorbis which was browsing upon the stem of a plant just under the shade of a broad leaf. He darted at this, seized it, and then, putting his tail out of water, for the purpose of taking in a fresh supply of air, moved slowly down, bearing the snail with him. He held it by his fore-feet, turning round the coil until the aperture of the shell was opposite his mandibles, then he began nibbling away at the animal. In vain did the poor mollusc try to withdraw within its shelly fortress, for the beetle picked off the edges of the shell bit by bit, so as to expose the body as fast as it was withdrawn. All the way down to the bottom of the tank was this process continued, air-bubbles rising to the top, and bits of broken shell falling, till the beetle with his burden reached a stone near the bottom, where I left him still busy at his work.’

This puts the matter beyond doubt, if any before existed. I at once wrote to Mr. Tegetmeier to let him know that my experiments had, unknown to me, been anticipated, long ago, by Mr. Sowerby. Had he rescued his Planorbis shell, it would have compared very well with those forwarded to the Field office in 1893. They had been exhibited at the Malacological Society, and no one was able to solve the mystery of their mutilation. This shows, to quote the Field[10] on the subject, ‘how easily statements that have been recorded may subsequently be overlooked and entirely forgotten.’

To return to our Beetle. The male is a handsome creature, from an inch to an inch and a quarter long, clad in olive-green, bordered with yellow, and exceedingly active. His mate is smaller, more soberly clad in brown, without the yellow markings, and the wing-cases are more or less furrowed.

The first thing to notice is the shape of the body, oval and smooth, offering no resistance to the water. The hind pair of legs are flattened and fringed with hairs, so as to make capital paddles. In swimming the right and left legs are moved together.

Now, though this Beetle lives in the water, it is made, so far as concerns its breathing apparatus, after the fashion of a Land Beetle, and consequently is compelled to come to the surface pretty frequently for a supply of air, which it obtains in this wise. Directly it ceases paddling it floats to the top of the water; and as the head is heavier than the tail the latter projects a little above the surface. Then the wing-cases are raised, and air flows in under them to the breathing holes on each side. The operation is not a long one, and as soon as it is over the Beetle is ready for another ramble round his dwelling-house.

But if we do not supply our captive with food that he may take for himself, it is only right that we should feed him, which may be done at intervals—say, every other day. ‘Little, and often,’ is an excellent motto to guide us in our feeding; and though its adoption may entail some trouble, it will be more than compensated by the success that will attend our endeavours to keep the inmates of our aquarium in good condition. And the operation of feeding our Beetle will show us that he has some capital sense-organs, which are of as much, if not of more, use to him than his eyes.

He is a flesh-eater. Let us take a small piece of meat or fish in a pair of forceps, or stuck on a pointed stick, and hold it at a little distance from his great eyes. The chances are that he will not see it. Even if we put it in front of him, he is quite likely to disregard it, for he has nothing corresponding to a nose, with which he may smell. From his head there spring a pair of long feelers—the antennae—and by means of these we will let him know that his dinner is ready. That is effected by drawing the food along the side of one of the antennae. The creature undergoes a sudden change. Till the antenna was touched with the food he was resting on his swimming legs. But in a moment down goes his tail and up goes his head, he stretches out his raptorial legs, and clutches wildly at the forceps or stick, as the case may be, holding so tight that he may be dragged round and round the glass vessel. Let go he will not, of his own accord; and it would be a difficult matter to shake him off. Similar experiments may be tried with other Beetles, and the result will be to impress on the mind the fact that the feelers are capital sense-organs.

If we are to turn our Beetle to the best account, we shall need to handle him. It may be inconvenient to wait till he dies, so we will kill him quickly and painlessly by plunging him into boiling water, and he may be preserved by putting him into a tube containing about equal parts of water and spirit, or a five per cent. solution of formalin.

Dissections should properly be made under water. The Beetle should be fastened, back upwards, to a piece of cork weighted with lead, and placed in a deep saucer, or dissecting dish, and covered with water. But a good deal of rough dissection, as is ours, may be done in air, and the Beetle may be fastened to any convenient piece of board, or even held in the palm of the left hand. Very little practice is needed to run over the external parts of a large Beetle in this manner.

Fig. 17.—Outline of Dytiscus (male). a, antenna; b, maxillary palp; c, eye; d, fore-leg; e, thorax; f, middle leg; g, elytron; h, suture; i, hind leg; j, claw; k, tarsus or foot; l, tibia or shank; m, femur or thigh; n, first three joints of foot, widened into a plate with suckers beneath.

First, let us look over our Beetle, and get some general notions of its make. As it lies, back upwards, it is clear that it consists of three parts or regions — —— ———, the first of which is the head, the second the thorax, and the third the abdomen. Not only in our Beetle, but in Insects generally, these parts correspond to the words that denote them, in that the thorax is longer than the head, and the abdomen longer than the thorax, as shown by the three dashes, a few lines above.

These divisions are well shown in Fig. 17, where other parts are also marked. It will pay to go over our own specimen with this figure before us, and so make acquaintance with the several parts, to some of which we shall return in greater detail.

Fig. 18.—Male Dytiscus in flight.

At this point, if we have not done so before, it will be convenient to fasten our Beetle, in the position figured, by a stout pin driven between the thorax and the abdomen, just above the suture (h). We want to raise one of the wing-cases.

If a needle be taken in each hand, between the thumb and first two fingers, and that in the left hand be used to steady the creature, the wing-case on the right may be raised with the needle in the right hand, and then cut off. The small filmy membrane, of somewhat triangular shape, which comes off with the wing-case, is the winglet. There is one on each side; and their vibration causes the humming noise made by these insects in flight. When the water dries up in one pond, or food becomes scarce, they will leave and fly off to another.

The wing lies folded upon the abdomen. A good deal of very interesting matter has been written on the way in which Insects fold their wings, but we can see for ourselves how this Beetle folds them. All we have to do is to take the wing, and draw it gently away from us, and so unfold it. We may use finger and thumb, or a small pair of forceps. When let go, it will spring back to its old position. Reference to the expanded wing in Fig. 18, and to the diagrams Figs. 19 and 20, will show how the wing is folded.

Fig. 19.—To show fold of (right) wing of Dytiscus.

Fig. 20.—To show fold of (right) wing of Dytiscus.

The cross-mark in the diagram represents a joint in the chitinous rod that forms the wings. This lies just above the cell (which is left white in Fig. 18). The shorter part of the rod is bent down, forming an acute angle (Fig. 20); of course, carrying with it the membranous part of the wing.

This may seem a little difficult. But if it be tried on a specimen, no real difficulty will be experienced. When the wing has been unfolded, it will, if let go, spring back to its old position, the shorter part lying underneath, and the chitinous rod fitting into a groove formed by the projecting sides of the segments of the abdomen.

To this point the sum of our knowledge about Dytiscus amounts to this: It is aquatic in habits; its body is divided into three regions; and it has a pair of membranous wings, covered by chitinous wing-cases, or sheaths, technically called el´ytra (each being an el´ytron). Wing-cases of this kind are the distinguishing mark of the Beetles, or Coleop´tera, though they are not always so well developed as in the specimen with which we are dealing. This we can discover for ourselves by examining all the Land Beetles met with in a country ramble or in a stroll round the garden.

Now let us unpin our Beetle, turn it on its back, and examine it from the under side. Head, thorax, and abdomen may be made out more clearly than before, and we can see that the last two regions are divided into segments.

Let us deal with the head first. This may be easily separated from the thorax with a dissecting needle, or with a pocket-knife—an exceedingly handy tool. The huge goggle-eyes cannot escape observation; and, even without a magnifier, they may be seen to be compound—that is, made up of a number of facets, which show like a fine network.

Just in front of the eyes are the antennae, which serve as organs of touch and perhaps also of other senses.

Kirby has recorded facts which seem to show that the antennae (in some cases) are also organs of hearing. Other authorities, after many observations, have come to the same conclusion. The matter, however, is beset with difficulty. It is certain that some Insects have their ears in their legs; and for the present, at any rate, we may be satisfied to know that the antennae are sense-organs, certainly of touch, probably of smell, and, in some cases, of hearing. An excellent authority on the subject is Sir John Lubbock’s book, The Senses of Animals[11], which contains references to very many original papers.

Fig. 21.

Fig. 21.—Upper surface of head of Dytiscus. a, labrum, or upper lip; b, clypeus or shield; c, mandible dissected out, and (d) reversed; e, eye; f, antennae.

Fig. 21a.

Fig. 21 a.—Under surface. a, mentum or chin; b, ligula or tongue; c, labial palp; these three together forming the labium, or lower lip; e, eye; f, antennae. Above the maxillae, or lower jaws (d d), are shown dissected out: d¹, inner or palpiform lobe; d², maxillary palp; d³, lacinia or blade; d⁴, the palpifer or piece that bears the palp (d²); d⁵, stipes or stalk; d⁶, the cardo or hinge.

Now we may pass to the mouth parts. It will be good practice to dissect these out, either in air or in water. We may hold a Beetle between the finger and thumb of the left hand, and separate all the parts with a needle held in the right. It is a good plan to gum these parts on a card, for comparison with the figures in our favourite book—whatever that may be—on Natural History, and also with the mouth parts of insects of other Orders. For however much these may differ in form, and in the uses to which they are put, they are really modifications of the same parts.

In Fig. 21 we have the upper side and in Fig. 21A the under side of the head represented, so that we may easily get acquainted with the different parts, and the names given to them. The cut should be gone over several times, and the parts in the picture compared with those in the specimen under consideration. It is good practice to endeavour to draw what is seen from the specimen itself, and then to compare the result with the work of the trained artist. And the mouth parts of Dytiscus may be compared with the mouth parts of the Cockroach (Fig. 33).

Fig. 22.—Disposition of mouth parts.

Returning to practical work, the first thing is to separate the labrum, or upper lip, from the head. Then the large mandibles should be dissected out, and cleaned (by soaking in caustic potash) from the muscles which will come away with them. Behind these are a smaller pair of jaws, the maxillae, furnished with a pair of palps, called maxillary palps from their position. These are to be dissected out; and then the lower lip, or labium, may be separated by passing a sharpened needle along the line where it joins the chin. The palps on the lower lip are called labial palps.

When these parts are cleaned and dried, they should be gummed on card, as shown in Fig. 22, where the long lines represent the upper and lower lips respectively, and the shorter ones the mandible and maxilla of each side.

So much for the head. Now we discover that what appeared to be the thorax, when we were looking at the upper surface of the Beetle, and what is called the thorax in descriptions of Beetles, is really but a portion of that region, which is seen to be divided into segments. The covering on the upper surface protects only the first segment, the middle and hinder ones being covered by the wing-cases and the scutellum (a triangular piece jutting backward from the second segment, and meeting the suture). This is not represented in Fig. 17; but we may put in with our pen a tiny triangle, with its base towards the head, and its apex towards the tail—this will meet the case.

The first segment bears no appendage above, but to the under side is attached the first pair of legs. The middle segment also carries a pair of legs, and on its upper surface are the wing-cases, to the under side of which, and to the body, the winglets are joined. The last segment bears the wings above, and the last pair of legs below, these being placed very far back, so as to give them greater power in propelling the animal through the water.

It will be convenient to examine the legs next. First, however, it will be well to look at a normal leg of an Insect (the Cockroach), and learn the names of the different parts. First comes the coxa (a) or haunch, next the trochanter (b), then the femur (c) or thigh, the tibia (d) or shank, and the tarsus (e) or foot, ending in a pair of claws. There are three pairs of legs in perfect Insects, and usually the same number in larval forms, though in some of these legs are entirely wanting.

Fig. 23.—Leg of Cockroach.

In the males of the Margined Water Beetle and many of its near relations the first pair of legs deserve special attention. The first three joints of the tarsus have coalesced to form a disk or cup, which in our specimen bears two smaller ones on its inner surface. A power of 20 will show the disk nearly as well as it appears in Fig. 24. The purpose of this disk, or clasper, which is absent in females, is obvious. It was formerly supposed to act as a sucker, but Professor Lowne and Professor Miall[12] have shown that it does not act by atmospheric pressure, but by a viscid secretion discharged from the cup-like hairs with which the inner surface is set.

Fig. 24.—Tarsus of Dytiscus (magnified).

The middle pair of legs in the male also bear cup-like hairs on the corresponding joints of the tarsus, and in very much greater number. Professor Miall quotes Simmermacher to the effect that while the large disk on the fore-leg has 170 sucking-hairs, the enlarged joints of the tarsus of the middle leg bear no less than 1590. These hairs are plainly discernible with the half-inch Steinheil, and I have made them out with the inch, and think that I could show them to anybody else with that power. I have not looked for these sucking-hairs on the middle leg of other Beetles of the same family which have disks on their fore-legs, but they do exist in some other genera.

If we watch a male Dytiscus in life, in a small aquarium, we shall soon be convinced that Lowne and Miall are correct in their statement that the cup-hairs discharge an adhesive substance. We shall see this all the more plainly if there is much floating vegetation. For, in swimming about, the Beetle will often come in contact with some of this, and it will adhere to the cup-hairs. His struggles to free himself from the encumbrance will show that the attachment is not altogether under his control. The offending weed is rubbed against the spines of one of the other legs till it is removed.

Fig. 25.—Female Dytiscus swimming.

The spines with which the legs are set are worthy of a good deal of attention, and, like the adhesive cup-like hairs, though in different fashion, they doubtless assist the animal in holding its prey. The first and middle legs end in strong claws; those of the last pair are not so well developed.

The last pair of legs are the swimming organs. The tibia and tarsus are fringed with long stiff hair behind, so as to hold the water when the Beetle swims. A peculiar arrangement of the first joint of the tarsus allows the edge to be presented to the water when the limb is carried forward for the return stroke, thus offering the least possible resistance. This Dr. Sharp has compared to the action of a rower in feathering his oar. There is, however, this difference, which it is well to note. The oar is feathered after the stroke; the Beetle feathers its legs before the stroke. It is the first motion when it begins to swim, and the action is not peculiar to the male.

We now come to the third region, the abdomen. Like the thorax it is visibly divided into segments, though the division between them is not so great. Much difference of opinion exists as to the number of segments in the abdomen of a typical insect. Some authorities maintain there are eleven, while others put the number as low as five. This, however, is theoretical rather than practical. It is enough for us to know that the number apparently varies greatly, owing to the coalescence of two or more of the segments.

Fig. 26.—Upper surface of abdomen of typical Beetle.

The head in Insects, we have seen, carries the eyes, antennae, and feeding organs. The thorax bears the legs and wings. The abdomen bears no appendages, except in some cases, on the last segment; these are called cerci. It may be, however, that the stings of bees and the ovipositors of saw-flies and other insects are modified appendages.

On examining the abdomen of Dytiscus we shall probably be struck with the difference in appearance between the upper and the under surfaces. The latter is hard, smooth, and shiny; the former, when the wings are removed, is seen to be covered with felt-like hair.

Our interest is with the upper surface. Along the abdomen on each side lie spiracles, stigmata, or openings to the breathing tubes. The first and last are larger than the rest, and their general form can be readily made out with an inch magnifier, and with the half-inch we may get some idea of the detail shown in Fig. 27.

Fig. 27.—Spiracle of Dytiscus (magnified).

Dytiscus breathes in this way. Floating up to the top of the water, the end of the abdomen projects above the surface. If one watches the Beetle the wing-cases will be seen to rise a little. The air retained by the felted hairs is given off, and a further supply taken in. Then the wing-cases are lowered again; the Beetle gives two or three strokes with its swimming legs, and descends below the surface to ramble round the tank in search of food.

Fig. 28.—Tracheal tubes (magnified).

This air-supply between the wing-cases and the abdomen is taken in at the spiracles and distributed through the tracheal tubes throughout the body. These tubes branch and subdivide till they end in small twig-like vessels comparable to the capillaries of the human body. They consist of two layers—the inner strengthened by what probably is a spiral fibre, though Packard believes that, in some cases at least, it consists of similar rings. But we must not pursue this subject. It would lead us beyond our appointed limits.

Another Beetle fairly common in stagnant waters round London and in the southern counties is that to which the name Great Water Beetle (Hydroph´ilus pic´eus) of right belongs. This name is sometimes wrongly applied to Dytiscus, with which its rightful owner has little in common, except its aquatic habitat. Its scientific name is Hydrophilus piceus; but we shall speak of it as Hydrophilus.

It is not a very easy matter to take this Beetle with a net, by sweeping in the ordinary way, for it likes to get into the middle of a mass of vegetation, where it is sure of a good food supply, and is probably safe from the attacks of Dytiscus, who not unfrequently makes a meal of his larger relation. A good plan is to pass the net under a mass of weed and then shake it to and fro in the water. By this means any Beetles in the weed will be dislodged from their hiding-places, and fall down into the bottle.

They have, in confinement, the same habit of making a snug place for themselves; and more than once I have fancied that a Beetle of this species had escaped from the aquarium, when all the time it was hidden in a thick patch of water-moss. They are practically vegetable feeders, though Dallas says that they are not such strict vegetarians as to deny themselves a meal of animal food when they meet with a dead mollusc or larva in the course of their wanderings. I have never known them to indulge in animal food, dead or living, but I have known them refuse it.

Hydrophilus is the largest British Water Beetle, and, with the sole exception of the Stag-Beetle, the largest British member of the Order. Its total length is very little less than two inches, and across the middle of the back it measures about half as much. It is more slenderly built than Dytiscus, and the contrast in the size and armature of the legs is very striking (Fig. 29). There is also a great difference in their method of progression through the water. Dytiscus moves both legs simultaneously, while Hydrophilus walks rather than swims, moving one leg after the other.

If we cannot collect this Beetle for ourselves—which we should endeavour to do, if possible—it may be bought of almost any dealer in what are called ‘aquarium requisites.’ But prices rule higher for Hydrophilus than for Dytiscus. Bateman says that this species is rarer than formerly, and that specimens cost from 1s. to 2s. 6d. a pair, ‘according to the dealer and the season.’ From this I gather that I must have gone to a shop where the prices were reasonable, for I have never paid more than 6d. for a Hydrophilus, and then have been allowed to pick out a male. At the same shop I have paid 2d. for Dytiscus.

Fig. 29.—Great Water Beetle. a, male; b, female; c, larva; d, pupa.

In keeping this Beetle we shall need a larger vessel than was required for Dytiscus. (In both cases the aquarium should be covered, for if food be scarce, and sometimes for other reasons, both these Beetles may take to flight.) The aquarium should be well supplied with growing water-weed, but none that is choice or valuable should be put in, for in moving about over the weed the animal will damage almost if not quite as much as it eats. This difficulty can be easily got over by supplying it with anacharis, water-crowfoot, milfoil, or any other common plant that grows rapidly and is easily procurable.

The only specimen that I have taken myself was captured a few miles north of London. It exhibited a strange instance of depraved appetite. In the large tank into which it was put were growing vallisneria, frog-bit, and water-crowfoot in plenty. These it was never seen to touch. The tank, at one time, had been used for newts, and floating on the surface was a piece of virgin cork. It had served the former inmates as a kind of island continent, and had never been removed. To the under side of this the Beetle would moor himself, head downwards, and nibble away, as if cork were the natural diet of a British Water Beetle.

In a few days the Beetle died. It was put into spirit, and soon after became the subject of a post-mortem. But its strange diet was not the cause of its death, which was sufficiently accounted for by injuries inflicted before its capture, probably by a larval or an adult Dytiscus.

It would be mere waste of time to go over this Beetle and describe it point by point, as was done with Dytiscus. If what was there written was of any value, readers will be able to apply for themselves the method laid down. There are, however, some points of difference to which it will be well to invite attention.

It is a good plan to lay specimens of these Beetles side by side for comparison. Hydrophilus is the larger of the two; and differs in colour as well as in size. Its hue is black with an olive tinge; and in certain lights a blue-black metallic gloss may be seen on the outer margins of the wing-cases. These are marked with faint longitudinal lines, and each bears three rows of dots running in the same direction.

The greater length and more slender build of the legs of Hydrophilus are at once apparent. There is also a marked difference in the tarsal joints of the fore-legs of the male. The disks and cup-like hairs of Dytiscus are absent in Hydrophilus, but in their stead the last joint bears a sub-triangular plate, studded on the inner surface with spines, which probably serve a similar purpose. A great deal of valuable information about organs of this kind and their functions will be found in chapter X of Darwin’s Descent of Man. Simmermacher’s paper[13] should be consulted by all who have the opportunity. Our inch magnifier will show us these spines quite clearly; and also a curious little bunch of bristles, which Simmermacher says are probably organs of touch.

It is a good plan to take Hydrophilus out of the water, and lay it upon its back, so that the difference between it and Dytiscus may be clearly seen. The Beetle should be handled carefully, for on the thorax is a kind of keel, ending in a sharp spine, which extends over part of the abdomen. This spine is free, and may easily wound the hands of those who do not watch the motions of the creature pretty carefully. The fore part of the abdomen and the thorax are covered with short close hairs, and when the Beetle is in the water these parts entangle a layer of air, which gives it the appearance of being covered with quicksilver.

The two Beetles differ also in their method of exchanging impure for pure air. Dytiscus, as we have seen, takes in a fresh supply under its wing-covers behind; Hydrophilus takes in a fresh supply in front, employing for this purpose the antennae, which apparently do not function as feelers, as is generally the case.

When Hydrophilus wants to take in a supply of pure air, it rises to the top of the water, slowly and deliberately. Unlike Dytiscus, it is never in a hurry. Then one of the antennae is pushed through the surface film, thus communicating with the air, which descends to the hair-covered thorax, whence it reaches the spiracles on the upper surface of the abdomen. To allow of this the wing-cases are slightly raised in front. The spiracles in Dytiscus are larger at the posterior end of the abdomen: in Hydrophilus the largest spiracles are in front. This is what might be expected, from the method adopted in each case for procuring a fresh supply of air.

These Beetles have frequently bred in confinement; but no better account than that of Lyonnet has ever been given of the operation of the female in making her cocoon and depositing her eggs. As his account is not generally available, a condensed translation of it is inserted with his illustration.

Fig. 30.—Female Hydrophilus constructing a cocoon. (After Lyonnet.)

Lyonnet[14] wanted to find out how the female made the cocoons (Fig. 30), and this is how he set to work. He put some of these Beetles into a large aquarium, with a good quantity of water and some duckweed. On May 31 and the following day he noticed that one of the females was swimming about in every direction, as if in search of something. Thinking that this was because she had not the proper materials for her work, he then put into the aquarium some thread-like alga of a kind which he had seen attached to some cocoons, and on June 3 the Beetle began to make a cocoon, but soon gave up the task, apparently because she was troubled by other aquatic insects which had made a home in this weed. These intruders were removed, and the Beetle set to work once more. Lyonnet then noticed that, like a spider, she had her spinning apparatus at the posterior end of the body. She extended the last segments slightly, and opened the hindmost one, when he saw a nearly circular opening, in which was a whitish disk (Fig. 30A, a). On this disk were two little brown tubercles side by side, nearly at right angles to the longitudinal axis of the body. From each there projected a blackish-brown conical tube, about a line long, stiff towards the base, but flexible and elastic towards the tip. These tubes were the spinnerets, which acted together with a parallel movement, and from each proceeded a separate thread.

And this is how she made her cocoon. She lay near the surface of the water back downwards, the under part of the body and the second and third pair of legs buried in the thread-like weed. The front legs were free, and with these she shaped the weed over her abdomen. Then she spun a covering of white silk against the under side of the weed. While she was spinning, from time to time she used her front legs to press and flatten the work against her body (Fig. 30B), giving it the shape of a flattened arch, to which her body gave the requisite curve. This, forming the top of the cocoon, was finished in about half an hour. Then she turned (Fig. 30C), and spun the bottom of the cocoon, moulding this, like the top, on the curve of her abdomen, and uniting the top and bottom with silk which she spun. The work occupied about an hour and a quarter.

The Beetle then remained nearly in that position for some two hours. At first she was hidden in the cocoon quite up to the thorax. The body, however, was withdrawn almost imperceptibly. During this time she was busy laying her eggs in regular order, with the pointed ends upwards.

After this she came out of the cocoon, and closed the mouth (Fig. 30D), making the opening smaller by degrees. Then she made a little mast (Fig. 30D, b), of the use of which Lyonnet admits his ignorance, suggesting, however, that its construction may serve to use up the silky matter remaining after the work is finished, lest it should acquire harmful qualities in the body of the Beetle. The true explanation seems to be that it serves to convey air to the eggs inside the cocoon.

On July 17 Lyonnet was rewarded for his patient watching by seeing a larva come out of the cocoon, and the next day some fifty more appeared. What he saw and recorded it is in the power of others to see, if they will imitate his patient observation.

The Cocktail Beetle, or Devil’s Coach Horse (Ocypus olens), is an excellent specimen of a Land Beetle to examine, for it is of fairly large size and extremely common. Moreover it does well in captivity, so that there will be no difficulty in watching its habits in life, and pickling it for closer examination when dead.

During the day these animals usually lie concealed under stones or pieces of earth, coming forth at dusk and during the night in search of food. Occasionally, however, they may be met with in daylight, leisurely stalking a smaller beetle or a fly; then with a dash seizing the victim in their powerful mandibles, which are quite capable of making an impression on the human skin, as those who handle these Beetles unwarily will discover for themselves.

Fig. 31.—Cocktail Beetle. a, larva; b, pupa.

Nothing of an animal nature comes amiss to them, and if they cannot capture living prey, they will make a hearty meal off carrion. This is an advantage to us, for we may feed our captives with dead insects or with small pieces of meat.

This Beetle is about an inch long, and of a deep dull black colour. The head is joined to the thorax by a distinct neck, and the abdomen is naked, owing to the fact that the wing-cases are very short. Its wing-cases bear about the same proportion to those of the Margined Water Beetle that a man’s frock-coat bears to a boy’s Eton jacket. And this Beetle may be taken as a good type of a group—the Beetles with short wing-cases (Brachel´ytra).

The attitude of this animal when irritated or alarmed is well depicted in Fig. 31. It raises its head menacingly and opens its strong mandibles to their full extent, at the same time turning up the end of the abdomen, like a scorpion about to sting. From the last segment it will often put forth a pair of white vesicles, from which is discharged a volatile liquid of disagreeable odour, that probably acts as a defence against insect-eating creatures.

The best way to capture one of these Beetles is to pick it up with what Kirby calls the ‘natural forceps’—the finger and thumb. It may be dropped into any convenient receptacle; the small metal boxes in which vestas are sold will answer the purpose very well.

My specimen was given me by a friend, who kept it with another in a round tin box. It lived with me for about three months in a four-ounce bottle, that measured three inches in height, to the neck, and two inches in diameter. The bottom was covered to the depth of about an inch with garden soil, and the top tightly corked, to prevent the prisoner’s escape. This precaution was necessary; for the inside of the bottle, though cleaned from time to time, soon became covered with a coating of earthy particles, which afforded the Beetle a pretty firm foothold.

It was an extremely interesting pet, and its struggles to escape by climbing up the sides of the bottle often afforded me much entertainment. It seemed to have a glimmering notion that the only way out was by the top, and knowing nothing of the cork it would rear itself up against the side, and try to climb up by vigorous movements of its fore-legs. It would also take advantage of any little lump of earth projecting about the rest. It had not intelligence enough to make anything like a mound for itself, though the inequalities were probably the result of its burrowing under the surface. Its temper was none of the best, for if it was disturbed with the forceps it would resent it fiercely. The mandibles would be opened, the abdomen curled up, and out would come the two vesicles as a means of defence. If the forceps were put near the mandibles, they would be seized, and the Beetle would hold on so tenaciously that it has often been lifted out of its bottle in this fashion.

It was exceedingly voracious, and was generally fed on garden worms. After a full meal its increase in size was very evident. This is not to be taken to mean that insects grow after they have attained the perfect or imago state, for this is not the case. But when they have had a long fast, the segments approach each other, and are forced apart when the creature is gorged with food. If a Beetle of this species were kept fasting for some days, and then carefully measured, and measured again after being plentifully supplied with worms or flies, there would be a difference of some millimetres between the results.

Dallas has an interesting passage in his Elements of Entomology respecting the boldness of the larval form, which is worth quoting. ‘I have seen one engaged in a struggle, which lasted about twenty minutes, with a worm of some five inches in length, the larva being scarcely more than an inch long. During this contest the little savage crept under the worm, fixing his mandibles into the creature’s body in various places, each bite apparently producing a considerable swelling. Sometimes he would fasten upon the head of the worm, and retain his hold with the pertinacity of a thoroughbred bulldog, although twisted about in every direction by the struggles of his intended victim. At last, however, he seemed to come to the conclusion that he had been too ambitious in his desires, and went quietly off amongst the grass, rather prematurely, as it seemed to me, for when the worm began slowly to leave the field of battle, about an inch of his tail was attached to the rest of his body solely by the intestine, a union which the jaws of the larva would easily have dissolved.’

I have never seen a fight between a larva and a worm, for the few larva I have kept have been fed on flies. But the adult Beetle which has once fastened on a worm cannot be shaken off. It will grip its prey with the first pair of legs, fixing the claws in the skin, and will finish a worm three inches long at a meal.

A dead specimen should be looked over in the way recommended for Dytiscus, raising the small wing-covers and unfolding the wings. The spiracles are to be looked for at the sides of the abdomen, in the groove formed by the meeting of the upper and under plates of each segment. The short downy hair with which the body is covered should be noticed, and the front legs are well worth examination. The tibia or shank is armed with a strong spine, and between this part of the leg and that which follows it is a notch, through which the Beetle passes its antennae to clean them from dirt. The peculiar shape of the joints of the tarsus or foot is very plainly discernible with the appliances at our command, and by a careful management we may make out the different kinds of hairs with which four out of the five of these joints are furnished; some stout and spine-like, others finer, ending in a pear-shaped bulb. These last probably serve the same purpose as the sucking-disks of Dytiscus and the tarsal plates of Hydrophilus.

CHAPTER III
COCKROACHES; EARWIGS; THE GREAT GREEN GRASSHOPPER; THE WATER SCORPION; THE WATER BOATMAN; CORIXA.

The next insect to come within range of our pocket lens is the Common Cockroach (Blatta orienta´lis[15]), popularly misnamed the Black Beetle. We shall have no difficulty in procuring material for examination. Housekeepers will tell us that these creatures are only too plentiful.

In the last chapter we dealt with Sheath-winged Insects—the Coleop´tera. Cockroaches belong to the Orthop´tera, or Insects with Straight Wings. The mouth-parts resemble those of Beetles. The chief differences that mark off the Cockroaches and their kin from the Beetles are the incomplete metamorphosis which the former undergo, and the character of the wings. Straight-winged Insects, when they leave the egg, differ little in shape from the adult, except in the fact that they have no wings; and these appendages are absent, or so small as to be useless for flight in many species. When wings are present the first pair are of little or no use for flight. They are not, however, hard chitinous sheaths, meeting in the middle line—that is, straight down the centre of the back—but of a flexible leathery or membranous substance, and they usually overlap each other at the tips. The hinder wings are large and nearly semicircular. The principal veins radiate from the centre to the circumference, like the sticks of a fan, and when the wings are folded up they lie straight along the upper surface of the abdomen. It is from this fact that the Order derives its name.

There are two great groups, or sections, of Straight-winged Insects—those that run, like the Cockroaches, and those that leap, like the Grasshoppers. No Straight-winged Insect is aquatic.

The Common Cockroach, now so abundant, is not a native, but an importation from Asia; though how it reached this country is not quite certain, probably by way of Holland. It seems to have established itself in London by the end of the sixteenth century, and some two hundred years later we find Gilbert White recording (in or before 1790) that ‘a neighbour complained that her house was overrun with a kind of black beetle, or, as she expressed herself, with a kind of black-bob, when they got up in the morning before daybreak. Soon after this account I observed an unusual insect in one of my dark chimney closets, and find since, that in the night they swarm also in my kitchen.... The male is winged, the female is not, but shows something like the rudiments of wings, as if in the pupa state.... They are altogether night insects, lucifugae, never coming forth till the rooms are dark and still, and escaping away nimbly at the approach of a candle.’

This description leaves no doubt as to what the ‘black-bobs’ really were. This name seems to have dropped out of use, and it would be well if ‘black beetle,’ in the sense of Cockroach, were also allowed to drop, for the term contains just as many errors as words.

We may make our first acquaintance with these insects by keeping some specimens in confinement. A tin box, with a glass lid, will make a capital dwelling for them. Some paper should be put in, for them to hide in away from the light, and there can be no difficulty in providing them with food. ‘Bark, leaves, the pith of living cycads, paper, woollen clothes, sugar, cheese, bread, blacking, oil, lemons, ink, flesh, fish, leather, the dead bodies of other cockroaches, their own cast skins and empty egg-capsules, all are greedily consumed. Cucumbers, too, they will eat, though it disagrees with them horribly[16].’

We have Dr. Sharp’s authority for the statement that in confinement these insects are rather amusing pets, as they ‘occasionally assume most comical attitudes, especially when cleaning their limbs. This they do somewhat after the fashion of cats, extending the head as far as they can in the desired direction, and then passing a leg or an antenna through the mouth; or they comb other parts of the body with the spines on the legs, sometimes twisting and distorting themselves considerably in order to reach some not very accessible part of the body[17].’

The prejudice against these insects is, however, so strong, that most people will prefer to examine dead rather than living specimens, on account of the disagreeable odour of the latter. This odour is due to a fetid excretion from the mouth, and if the specimens are killed by dropping them into boiling water, this will be discharged, and after a little while they may be taken out with a pair of forceps, and put into spirit for preservation. If they are dropped alive into spirit, the excretion will communicate its strong scent to the preserving medium, and this should be changed before the insects are examined.

From Fig. 32 we may get a general idea of the appearance presented by a male or female, lying back upwards in a small glass dish, ready for examination with the pocket lens. The female may be distinguished at a glance by her wingless condition—only rudiments of wing-cases being present, and no wings—and her broader abdomen. In life she does not stand so high upon her legs as does the male, and her abdomen trails along the ground. The male does not acquire his wings till the last moult.

Female.Male.

Fig. 32.—Cockroaches.

As the Cockroach lies back uppermost in a glass dish, the head is almost concealed. This is especially the case, unless the insect is flattened out in some way, or pinned down to a piece of weighted cork. There will thus be, apparently, two, instead of three main divisions. This arises partly from the fact that the head is deflexed, or bent down so that the mouth is turned towards the rear, and partly because the first segment of the thorax bears a chitinous shield, roughly semicircular, which covers so much of the head as would otherwise be visible.

The difficulty, however, may be easily got over, by reversing the position of the insect, and raising the head with a needle. The antennae will attract attention by their great length. In the male insect they exceed, while in the female they fall a little short of, the total length of the body. They are well worth examination. Even a low power will show that they consist of a number of joints—usually from seventy-five to ninety. The three basal joints are much larger than the rest, and in the female the third basal is nearly as long as the first. All these joints are thickly set with stiff hairs directed forwards. At the outer side of each antenna is a compound eye, and on the inner side is a pale spot, the fenestra, which in the males of some foreign Cockroaches is replaced by a simple eye.

If Cockroaches are kept in confinement, and forced out into the light, the constant motion of the antennae will satisfy the observer that they are of great use to their owners. By means of these organs they not only discover their food, but become by some means, probably by the motion of air-waves, aware of danger that threatens them. Belt, in his Naturalist in Nicaragua (p. 110), speaking of the Cockroaches that infest houses in the tropics, says, ‘They are very wary, as they have numerous enemies—birds, rats, scorpions, and spiders; their long, trembling antennae are ever stretched out, vibrating as if feeling the very texture of the air around them; and their long legs quickly take them out of danger.’ It is not given to every one to visit the tropics, but we may all use our eyes in observing the common insects that abound in our country, and in doing this we shall strengthen the habit of observation, and very often find confirmation of what we read of the habits of insects in distant lands.

Sir John Lubbock[18], in treating of the sense of smell in Insects, says that ‘Plateau put some food of which cockroaches are fond on a table, and surrounded it with a low circular wall of cardboard. He then put some cockroaches on the table: they evidently scented the food, and made straight for it. He then removed their antennae, after which, as long as they could not see the food, they failed to find it, even though they wandered about quite close to it.’

The large kidney-shaped compound eyes are sure to attract attention. It is worth while to take out and break up an eye, gently washing out the pigment. If we do this, and then examine it with the pocket lens, we shall have some idea of the multiplicity of lenses in the eye of a Cockroach, each of the six-sided facets being a lens.

Next come the mouth parts, which may be run over very quickly, for those of Beetles are formed upon the same plan, and from this primitive plan are derived the mouth parts of all other Insects, of whatever character they may be. To examine the mouth organs the insect must be turned on its back, and the labrum (a), or upper lip, raised with a needle, so as to allow of a general view of the rest. Then the jaws or mandibles (b) may be picked out with a needle. These jaws are strongly toothed, and work from side to side, and it is easy to see that they are very efficient organs. The lower jaws (c), or maxillae, lie below, and are compound organs, each being made up of several parts—the base, called the cardo or hinge (not shown in the illustration, but connected at right angles by a joint with the lower part, the stipes). From the stipes rise the galea, or helmet, on the outer side; and, on the inner side, the lacinia, to which the name maxilla is often applied, though it properly belongs to the whole. At the base of the galea is inserted the five-jointed maxillary palp, thickly set with hairs, and probably an organ of touch.

Fig. 33.—Mouth parts of a Cockroach.

By examining the maxillae (c) before they are separated, and comparing them with the labium (c) or under lip, which closes the mouth from below, it will be evident that there is no slight similarity between them. Nor is this strange: for the under lip consists of the second maxillae joined at their bases, which form the submentum (s) and mentum (m). (The former is the small, the latter the large white basal portion; the vertical line in the illustration shows the mental suture, and should be traced in the dead insect.) The organs in the centre constitute the ligula; and on each side of the labium is a three-jointed palp (labial), like that on the maxillae, thickly set with hairs, and with a similar function. It is well to work over the mouth parts a few times till the relation between the maxillae and the labium is seen and understood. The internal tongue (d) is attached to the inner side of the labium.

Now, still working on the under side of the insect, the three segments of the thorax are to be made out, and one cannot fail to notice the great size of the first joint (the coxa) in all the legs, and that these joints seem to serve as shields to protect the under side of the thorax. Then the different parts of the legs should be traced, and compared with Fig. 23 on p. 44. The spiny armature of the tibiae is to be noticed, as are the claws, between which is a projecting lobe, though this is absent in immature specimens. We shall find that the appendages of the thorax are the same as in the Margined Water Beetle. It is well to take as little as possible on trust, and to verify everything that we possibly can.

Now we may reverse the position of our subject, and having cut off the wing-cases, which are technically called teg´mina, examine the wings. These may be gently unfolded with a needle or a camel’s hair brush, when the longitudinal method of folding will be clearly seen, and the difference of the veining from that of the wings of the Margined Water Beetle will be apparent. A female should also be examined, and the small tegmina cut off, so as to see that not even the rudiments of wings are present.

The Cockroach breathes like other adult Insects, and the spiracles are ten in number—two on the thorax and eight on the abdomen. The thoracic spiracles may be pretty readily seen, but those on the abdomen are not so easy to make out. But by cutting away, with a fine pair of scissors, the edges of the plates that cover the upper and under surfaces of the abdomen and the membrane that unites them (Fig. 34), we may discover them as the open ends of small tubes. While dealing with the insect in this fashion, it will be easy to take out a piece of the tracheal tube, which may be compared with Fig. 28.

Fig. 34.—Cockroach, showing Spiracles.

The abdomen consists of a series of rings or segments, the exact number of which is rather difficult to decide, from the fact that some are concealed and others altered in form. Dr. Sharp[19] says that ‘it is considered that ten dorsal and ten ventral plates exist, though the latter are not so easily demonstrated as the former.’ In the male, ten above (dorsal) and nine below (ventral), and in the female two less in each case, may be made out without dissection.

From the sides of the tenth segment two organs, the cerci (Fig. 35, a), are given off, one on each side. These may be distinguished from the styles of the males by their presence in both sexes. Our inch lens will show that each cercus consists of sixteen rings. If we use the half-inch, we shall see that each ring is set with hairs of different lengths.

When we have got so far it may be well to compare the structure of a cercus with that of an antenna (p. 67). In each we have a succession of jointed rings giving flexibility to the organ, and the rings in each case are studded with hairs. It has been shown pretty conclusively—and we may verify the experiments—that the antennae are sense-organs. Are we not justified in coming to the conclusion that, since the antennae and the cerci resemble each other in structure, they also resemble each other in function? If the Cockroach receives sensations by means of the antennae, is it not probable that it also receives sensations by means of the cerci?

Having worked over the Cockroach from the outside, it will be advantageous to get some acquaintance with its internal anatomy. This is not a difficult matter. The specimen is to be pinned down, under water, with its back uppermost. The wings having been removed, a longitudinal cut is to be made down the centre from the posterior part of the abdomen to the back of the head, and the two sides of the integument turned back. Or the junction between the upper and lower plates on each side may be cut through with a cutting needle, and the whole integument removed.

The first task is to clear away the fat-body, a whitish substance which overlies the chief organs of the body. When this is picked to pieces and floated off the digestive system will be exposed. After this has been worked over a few times there should be no difficulty in dealing with similar parts in other Insects. At the back of the head lies the gullet or oesophagus leading into the crop (c), at the base of which lies the gizzard (g). The interior of this organ is furnished with six strong chitinous teeth, with small ridges of the same substance between them. Towards the posterior end are six cushions, all set with fine bristles. Behind this comes the stomach (v), into which open seven or eight tubes, closed at one end, and between it are the Malpighian tubes, which are concerned in the process of excretion. The small intestine (co) succeeds, and behind this is the rectum (r).

Fig. 35.—Alimentary Canal of Cockroach.

It will be interesting to separate the gizzard from the crop (c) and stomach (v) and break it open with a couple of needles, so as to examine the teeth, which will be more easily made out if the opened organ be allowed to soak for a time in a solution of caustic potash.

Similar teeth-like processes are found in the gizzards of many other Insects, and their presence has given rise to some strange ideas. Swammerdam[20] says, ‘I preserve also the threefold stomach of a locust, which is very like the stomach of animals that chew the cud, and particularly has that part of the stomach called Echinus[21] very distinctly visible. I do not, therefore, doubt but locusts chew the cud, as well as the animals just mentioned. Indeed, I persuade myself that I have seen this.’

Somewhat similar teeth-like processes exist in the Lobster, the Crab, and the Crayfish. ‘Professor Plateau has expressed a strong opinion that neither in the stomach of Crustacea nor in the gizzard of Insects have the so-called teeth any masticatory character.’ He adopts Swammerdam’s comparison, but considers them strainers, not dividers of the food[22].

We may be fortunate enough to meet with some specimens of the American Cockroach (Periplane´ta america´na, Fig. 36), a much larger species, which has established itself in some few places in this country. At the Zoological Gardens, Regent’s Park, it is abundant, and has almost, if not entirely, driven out the common form. Mr. Bartlett believes that it was introduced in cases in which animals have been sent over from America. Both sexes are winged. They not only possess organs of flight, but use them. If one visits the Gardens, there will be no difficulty in getting specimens; and it is interesting to compare the points of agreement in and of difference between this animal and our common form.

Fig. 36.—American Cockroach (male).

The Earwig (Forfic´ula auricula´ria) is common enough to furnish us with plenty of specimens on which we may employ our pocket lens. Any garden in the summer months will yield an ample supply. Earwigs, like Cockroaches, are light-shunning insects, and love to hide themselves in the corollas of flowers; and it is probably from their habit of seeking to conceal themselves that they have acquired their bad reputation—by no means confined to our own country—of creeping into the ears of persons lying asleep, and causing death by getting into the brain. Such an occurrence is beyond the bounds of possibility. No insect of this size could pass the drum of the ear.

We may easily keep these insects and observe their movements, if we put them into a wide-mouthed glass bottle and supply them with food. They are extremely fond of the flowers of the dahlia; but a dahlia would offer too many hiding-places, so we will put into the bottle some nasturtium flowers, or any others with a bell-shaped corolla.

If we get a colony in spring we may watch the care of the female for her eggs. According to Kirby and Spence[23], ‘she absolutely sits upon her eggs, as if to hatch them—a fact which Frisch appears first to have noticed—and guards them with the greatest care. De Geer (Mémoires, iii. 548) having found an earwig thus occupied, removed her into a box where was some earth, and scattered the eggs in all directions. She soon, however, collected them one by one, with her jaws, into a heap, and assiduously sat upon them as before. The young ones, which resemble the parents, except in wanting elytra and wings, ... immediately upon being hatched creep like a brood of chickens under the belly of the mother, who very quietly suffers them to push between her feet, and will often, as De Geer found, sit over them in this posture for some hours.’ Mr. Kirby adds: ‘This remarkable fact I have myself witnessed, having found an earwig under a stone which I accidentally turned over, sitting upon a cluster of young ones, just as this celebrated naturalist has described.’

Like the Cockroaches, Earwigs undergo an incomplete metamorphosis. When the young leave the egg they resemble their parents, as may be seen from the immature forms represented in Fig. 37. The resemblance becomes greater at each successive moult.

Fig. 37.—Larva and Pupa of Earwig.

In working over these insects, the forceps, or pincers, at the end of the abdomen will attract attention. They are found throughout the family, but little is known of their function. It is said that they are used to aid in folding the wings, and tucking them under the wing-covers. This can scarcely be their only function, for they are found in species that have no wings. Probably they serve as organs of defence and, to some slight extent, of offence. When the abdomen is curled up, these forceps certainly give the insect a threatening appearance. They cannot, however, do much harm.

These forceps differ in shape in the male (Fig. 38) and female, the blades being almost close together in the latter. In the males they differ considerably in size. Of 583 mature males taken in one day in the Farne Islands, and examined by Messrs. Bateson and Brindley, the forceps varied in length from 2·5 mm. to 9 mm.[24] These are called respectively ‘low’ males and ‘high’ males. The latter are in all points larger than the former, and have been described as a separate species, ‘but it was impossible to get reliable measurements of the total length, owing to the fact that the abdominal segments telescope into each other’ (cf. p. 30).

After examining the antennae and dissecting out the mouth organs, the peculiar overlapping or imbrication of the plates of the abdomen should be looked for; and on the membrane that connects them the spiracles may be detected.

The wings and the complex method of folding have led some systematists to rank the Earwigs as an Order, while some others rank them as a Sub-order. For the present, at any rate, we need not concern ourselves about this. It is enough for us to know that they are closely related to the Orthop´tera.

As we look at the Earwig from above, the wing-cases recall to our mind those of the Devil’s Coach Horse (Fig. 31), though there is one great difference. From beneath those of the Earwig project two small leathery pieces which are absent in the Beetle. These pieces are not, as one might imagine, at the tips of the wings, but on the front margin, about halfway down, and is indicated in the illustration by the shading between the extremity of the wing-case and the crease-mark at a.

Fig. 38.—Earwig (male).

From the illustration we may understand how the Earwig opens and closes its wings. From the point a veins, which are thickened about halfway down, radiate to the hinder edge of the wing, and a little beyond the thickening they are connected by a vein which runs parallel with the hinder edge. These radiating veins are brought together, so that there is a fan-like closing, like that of the Cockroach, but from a different centre. The wing is then folded back at the place where the veins are thickened, and then there is a second transverse fold at the point a, so that the only part of the wing now visible is the leathery patch, which projects beyond the wing-case when the wing is tucked away.

It is not difficult to unfold the wing of a dead specimen, under water, using a needle and fine brush. Mr. E. A. Butler[25] recommends a simple but excellent plan for unfolding and preserving the wing, by gumming it, with the upper surface downwards, to a piece of card, and gradually unfolding it and fastening it down. This is not so easy as it may seem, but with patience and perseverance success will be obtained; and a similar method may be adopted with the wings of other Insects, which may be mounted in this way without any trouble. Thus they may be easily preserved for examination at a future time, or for comparison with the wings of other Insects.

It is rather remarkable that an insect like the Common Earwig, which very rarely takes to flight, should have such a complex method of folding its wings. Dr. Sharp says that though the Earwig ‘is scarcely surpassed in numbers by any British insect, yet it is rarely seen on the wing. It is probable that the majority of individuals of this species may never make use of their organs of flight, or go through the complex process of folding and unfolding them.’

Let us choose our next example from the Leaping Orthop´tera. They may be distinguished at a glance from their relatives that run, but do not leap, by the peculiar structure of the third pair of legs. These are much longer and stouter than the other two pairs, and the thigh is very muscular. This insect is a very good type of the family Locus´tidae, to which, however, none of the insects popularly called ‘locusts’ belong. They are included in another family (Acridi´idae), where the common British Grasshoppers are also placed. The Locustids and the true locusts may be distinguished by the difference in their antennae: in the latter these organs are short, in the former they are very long and delicate.

The Great Green Grasshopper (Locus´ta viridis´sima) (Fig. 39) is fairly common all over the country, but often escapes observation from the fact that its hue corresponds so nearly to that of the foliage on or among which it lives. One specimen taken in a Devonshire lane gave me a great deal of trouble before it was secured and transferred to a small tube. It was perched on a leaf when I first saw it, and as I approached it leaped away. Though I was certain it had not gone far, it was some little time before I discovered it, and got near enough to grasp leaf and insect, in time to prevent the latter from taking another jump.

This insect may be kept alive in confinement for a considerable time, and will do fairly well on a diet of leaves and fruit, though it will not refuse an occasional meal of flesh. Dr. Sharp says that a specimen in confinement ‘mastered a humble-bee, extracted with its mandibles the honey-bag, and ate this dainty, leaving the other parts of the bee untouched.’ It is said that if two be placed together in a box they will fight most desperately, and that the victor will make a meal off the body of its victim. De Geer witnessed a case of this kind in a closely allied species that is found in Sweden. Its specific name signifies ‘wart-eater,’ and commemorates the fact that the peasants incite these insects to bite their warts, firmly believing that warts once bitten speedily disappear, and do not grow again. Westwood says that one of these insects actually devoured part of its own leg that had been broken off accidentally. When the creature was seen at night the detached leg was whole; in the morning about half of it had been eaten.

Fig. 39.—Great Green Grasshopper (female).

It is well to get specimens of male and female insects. We shall require the former in order to examine the sound-producing apparatus, which the females do not possess; and the latter for the sake of the ovipositor—a long scimitar-like organ by means of which the eggs are deposited. Let us take the female first. The length, including the ovipositor, is a little under two inches, and the antennae will measure about as much more. The wing-cases do not lie flat upon the back, as do those of the Cockroach, but in a slanting position, like the sides of a roof, forming a ridge in the centre. The head is not bent back, as in the Cockroach, nor does it project in front, as in the Beetles, but the front is almost vertical. The armature of the mouth is strong, and of the same pattern as that of the Cockroach. The hood—so the upper covering of the thorax is called—is of a peculiar shape, somewhat like that of a saddle. The wing-cases and wings, with their folding, will offer little difficulty. Next we may examine the cerci, and contrast them with those of the Cockroach and with the forceps of the Earwig. Last of all, the ovipositor must be examined, and its structure made out, so far as the means at our command will allow.

Apparatus of this kind for placing eggs in positions favourable to their development is by no means confined to these insects, for examples may be found in other Orders. Sirex, the so-called Tailed Wasp, has a long straight one, which is often supposed to be a sting, and the insect itself is not unfrequently taken for a gigantic wasp or hornet.

When the ovipositor of our subject is looked at with the unassisted eye, it appears to consist of two curved blades placed side by side, with an internal groove on each. The apparatus, however, is not quite so simple: it is made up of six chitinous rods, of which four—the two above, and the two central ones—are developed from the ninth segment of the abdomen, while the two lower ones spring from the eighth. It is not difficult to test these statements. Specimens are plentiful; and as the ovipositor in this insect is large, and easily broken up into its component parts, it may well serve as an introduction to the study of these organs in other Insects—the Saw-flies, for example.