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.