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.