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.

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.

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.

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).

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.

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.

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.

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.

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.

When the insect is about to deposit her eggs, she selects a spot where the soil is light, and bending the ovipositor nearly at a right angle to her body, thrusts it into the ground as far as possible. Then, by a muscular effort, the plates of the ovipositor are separated, and several eggs travel down the passage formed by the central pair of rods into the hole. This is repeated time after time, till the operation of egg-laying is completed. This takes place in the autumn, and the young emerge from the eggs in the spring. When they come out they are tiny copies of the adults; but they do not acquire wings till after several months. The ovipositor of the female appears after the second moult, and till this organ is developed no difference is apparent between the young insects.

The chief interest of the male insect lies in its wings, for the first pair (the teg´mina) are the organs with which it produces its ‘love-songs.’ Kirby comments on the fact that Lichtenstein, in the Linnaean Transactions (iv. 51), ‘draws attention to the eye-like area in the right wing-case of the males of this genus,’ adding that that author seemed ‘not to be aware that De Geer had noticed it before him, as a sexual character; and also, with good reason, supposed that it assists these animals in the sounds they produce.’

This is how De Geer (Mémoires, iii. 429) describes the sound-producing apparatus of the Great Green Grasshopper: ‘In our male grasshoppers, in that part of the right elytron which is folded horizontally over the trunk, there is a round plate of very fine transparent membrane, resembling a little mirror or piece of talc, of the tension of a drum. This membrane is surrounded by a strong and prominent nervure, and is concealed under the fold of the left elytron, which has also several prominent nervures answering to the margin of the membrane or ocellus. There is every reason to believe that the brisk movement with which the grasshopper rubs these nervures against each other produces a vibration in the membrane, augmenting the sound. The males in question sing continually in the hedges in the months of July and August, especially towards sunset, and part of the night. When any one approaches they immediately cease their “song.”’

It is probably unnecessary to do more than remark that the noises made by Insects do not correspond to the voices of the higher animals. ‘For no insect, like the larger animals, uses its mouth for utterance of any kind: in this respect they are all perfectly mute; and, though incessantly noisy, are everlastingly silent[26].’

Our plan with these wings is to first verify the fact of their bearing these talc-like spots, the serrated nervures on the right and the rudimentary file on the left elytron. The sound is produced by rubbing the base of the left elytron against that of the right. A recent author compares this insect to a fiddler, and says that the left tegmen is the bow and the right the fiddle.

The last point to examine is the ear. It seems strange to say that these insects have ears in their legs; but though some of the older entomologists regarded these structures in the tibiae of the first pair of legs as nothing more than resonators or sound-boards to intensify their chirping, there is no doubt that they are really organs of hearing. Much interesting information on this subject will be found in Sir John Lubbock’s Senses of Animals.

These oval patches are plainly distinguishable by the unassisted eye, and correspond in function to the tympanum or drum of the human ear. The air-supply to the tibiae is distinct from that of the rest of the body, and is derived from a large orifice on each side of the first segment of the thorax. These orifices may be seen by removing the ‘hood.’ Indeed, they cannot escape observation. From these orifices an air-tube passes to each leg, dividing into two branches in the tibia and reuniting below the drums.

Dr. Sharp[27] says that ‘although the tibial ears of the Locus´tidae are very perfect organs, there is great difficulty in deciding on the exact nature of their functions. They would appear to be admirably adapted to determine the precise locality from which a sound proceeds ... for the legs can be moved in the freest manner in every direction, so as to bring the drum into the most direct line of the vibrations. But as to what kinds of vibrations may be perceived, and the manner in which they may be transmitted to the nerves, there is but little evidence.’

The next Order from which we shall choose examples will be the Hemip´tera, containing the Land and Water Bugs and some other forms. Our chief concern, however, is with the Water Bugs. In this Order the metamorphosis is incomplete; the mouth is adapted for sucking the juices of plants and animals; and there are usually four wings. In the Land and Water Bugs, part of the fore wings is harder than the hind wings; in the other winged members of the Order both pairs of wings are membranous. The front wings are called hemel´ytra or halfel´ytra, to distinguish them from the el´ytra or wing-cases of Beetles, which are chitinous throughout. Fig. 41 shows the hemel´ytron and hind wing of a Land Bug, and the names given to the different parts of the front wing.

The Water Scorpion (Nepa cine´rea) is not difficult to procure, or to keep in confinement when it is caught. It would be straining language to call it a handsome creature, yet it well deserves careful study, on account of the wonderful modification of the first pair of legs, and it is from the resemblance of these to the pedipalps of the scorpion that the insect derives its popular name. Its length is about an inch and a quarter, from the tip of the beak, or rostrum, to the end of the breathing-tube. Its greatest width is a little over a quarter of an inch (Fig. 42). The general hue harmonizes well with the mud, but the upper surface of the abdomen is a warm red, ‘and is thick set with hair, so as to afford a very agreeable sight.’

It is extremely common in shallow pools, and its favourite haunt is near the shore, where it will lie, almost buried in the mud, with its raptorial legs elevated, ready to seize on any passing insect, and its breathing-tube just pushed through the surface-film. I learnt this habit of the insect on the first occasion on which I tried to collect specimens of it. I had been told that a certain piece of water swarmed with Water Scorpions. This, I afterwards found, was quite correct; but though I worked the pond from end to end, a single specimen was all that rewarded my labour. Whilst transferring the insect from the net-tube to the bottle for transport, a stranger joined me, and kindly volunteered his assistance. He had no collecting tackle, but in about a quarter of an hour he brought at least a dozen good specimens in the bottle he had borrowed.

It was natural to inquire to what his success was due. He told me that it was his first attempt at collecting, but that just before joining me he had noticed the ends of the breathing-tubes sticking out of the water. This excited his curiosity, and on moving the mud with his walking-stick, the insects were seen to crawl away slowly. When he saw me transfer the Water Scorpion from the net-tube to the bottle, he immediately recognized it. Then he courteously offered his help, for which, of course, I was grateful.

We may keep the Water Scorpion alive for a considerable time in a small bottle of water, in which is some growing weed. If we watch it moving about, we shall see that the front legs are used for locomotion as well as for seizing prey. Some authors doubt this. Any one may settle the question for himself, if he will put one of these insects into a small bottle with plenty of weed. Generally, however, the insect uses only the second and third pairs for walking, the first pair being raised and directed forward, with the tarsus bent at an angle (Fig. 42). Even when it does use its front legs for locomotion, the action is not that of walking; the insect employs these limbs to pull itself along in a sort of ‘hand-over-hand’ fashion, but on a level surface it uses the first pair in the same way as it does the other two pairs.

Its habit of burying itself in the mud may also be watched with very little trouble. A common pudding-basin will make an excellent aquarium for this purpose. The bottom is to be covered with garden mould and vegetable débris, mixed with a few stones. The whole mass should be arranged unevenly, so that when water is added it may not form one sheet, but a series of small shallow pools. Very little duckweed will serve to keep it sweet. It only remains to drop in the Water Scorpion. Before long it will accommodate itself to its new surroundings, and so bury itself that it will be no easy task to discover it.

An aquarium of the kind described stands at present on my writing-table. Many have been the inquiries as to what kind of creature lived therein; and more than one old hand at collecting has failed to find the insect. It is always safe to look round the sides of the basin for the breathing-tube; if it is not detected in this situation, a glance along the surface of the tiny pools will probably show a break in the film. The Water Scorpion will not be far off.

That the insect really does cover itself with mud may be demonstrated by transferring it from the aquarium described to any shallow vessel, and allowing a fine stream of water—say, from a dipping-tube—to fall gently on it. The mud will be washed away, and in a few seconds will settle at the bottom.

It is well to keep such an aquarium covered, for the Water Scorpion has no mean power of flight. A circular plate of glass, which may be bought for a few pence, makes the best cover, but a piece of fine muslin fastened round the rim of the basin will do. Swammerdam says, ‘These Water Scorpions live all the day in the water, out of which they rise about the dusk of evening into the air, and so flying from place to place, often betake themselves in quest of food to other waters.’ Then follows a deduction which shows how far he was in advance of his time: ‘This affords us a satisfactory reason for the great number of insects that immediately appear in the smallest collections of water, since they may very well get thither when it is dark, so that the opinion which ascribes to putrefaction the power of forming insects, &c., must, by this instance of the Water Scorpion’s nocturnal transmigrations, appear more and more frivolous and unnecessary.’

No larva or other animal that is of any value should be kept in the same aquarium with the Water Scorpion. Dr. Hill, who annotated the English edition of Swammerdam, says, ‘There is not perhaps in all the animal creation so outrageous or fierce a creature against those weaker than itself as the Water Scorpion. It destroys, like the wolf among sheep, twenty times as many as its hunger requires.’ The Rev. G. C. Bateman placed one in a saucer with a tiny minnow; ‘but no sooner did the little fish swim within reach of the fore-legs of the scorpion than it was seized by them, and pressed against the hungry creature’s rostrum.’ It seems to be particularly fond of Asellus, the water woodlouse. I have often taken dead specimens of this crustacean, sucked completely dry, from between the raptorial legs of the insect. One specimen was so thoroughly cleaned out that it was mounted just as it was, the only preparation being a brief soaking in spirit.

In examining the head the eyes may be readily distinguished, and on pressing the rostrum or beak with a needle, the proboscis will be forced out, just as one may force out the sting by pressing the abdomen of a bee or a wasp. In this group the antennae are three-jointed and concealed. When one begins to look for these organs he will probably come to the conclusion that the concealment is highly effectual.

A very simple method of finding them in a spirit specimen is to take the insect between the thumb and index finger of the left hand, holding it up to the light in such fashion as to keep the first pair of legs well clear of the head. Then, with a needle held in the right hand, raise the thorax till it lies in the same plane as the body. Each antenna lies in a groove beneath the eye. Gentle manipulation with the needle will lift them out, so that they may be clearly seen, not only with the hand magnifier, but with the unassisted eye. Or the insect may be pinned down under water instead of being held in the hand, and the antennae lifted or brushed out of the groove.

It will greatly simplify matters if, before attempting to raise the wings, the fact is borne in mind that the tip of the right wing-case lies over that of the left. It is perhaps as well to remove the wing-case altogether by inserting a needle under it, and gently raising it, using a little pressure in an outward direction. It will then be quite time to raise the wing and to see the method of folding and unfolding.