more troublesome, especially those which are inclined to take a ramble on certain mild days in search of food when none is at hand. Still there is no reason why even a beginner should not attempt the rearing of these. They will require food in the autumn until the cold weather sets in, and again early in spring as soon as the new leaves appear; but this is not of much consequence to those who reside in districts where the required food plants abound.
Wood feeders also require some special treatment and precautions, and the successful rearing of some is a matter of no little difficulty. A wooden cage is, of course, quite out of the question with these, unless you wish to test the power of their jaws. They must be kept in large pots or jars, covered over with wire gauze or perforated zinc, and supplied with fresh stems or logs of wood, or with moist sawdust fresh from their favourite tree. A few of them—the 'Goat' ([page 224]), for example—will eat dead and rotting wood, and may be fed on old palings and other waste providing the right kind is selected.
The troubles and disappointments of larva rearers are numerous and varied, and commence with the earliest moments of the young insects. Even the hatching period sometimes proves a trial, for it occasionally happens that the young larva has not sufficient strength to bite its way through the shell that surrounds it, and dies with nothing but the surface of its head exposed to view. This may be the result of keeping the ova in too dry a spot, the shell having become too hard and horny for the little creature's jaws.
Then the moulting seasons are always periods of trial to the larvæ, and often of loss to the rearer. Some of the hardier species may pass through all their moults without appearing to suffer anything more than a slight inconvenience at each, but in other cases the greater part of a brood may fall victims to these ailments of the growing stage.
Apart from these sources of loss, however, larvæ are subject to numerous diseases, infectious and otherwise, about which we know but little. A fever may rage in one of our cages; a fungoid growth may establish itself on the bodies of our pets, or we may see them cut down, one by one, through a fatal attack of diarrhœa.
In many such cases we are at a loss as to what to do. Blue pills and black draughts are not to be prescribed, and the modern practices of surgery and inoculation have not yet been applied to
insect patients with very great success; but we must do our best to adopt hygienic principles, paying the greatest attention to proper means of ventilation and to a regular and wholesome dieting. In the case of diarrhœa—a very common insect malady—the best we can do is to avoid the young and juicy leaves of the food plant, and substitute the older, and drier foliage.
Ichneumon flies have already been mentioned as great enemies of larvæ. These flies either deposit their eggs on the skins of caterpillars, or thrust their sharp ovipositors into the creature's flesh and lay their eggs beneath the skin. When the young ichneumons are hatched, they immediately begin to feed on the fatty matter that is usually stored in comparative abundance under the skin of the caterpillar, and thus they grow at the expense of their host, within whose body they lie completely hidden from view.
The poor caterpillar, though being eaten alive, often shows no external signs of the mischief wrought within, and, even though its substance is really decreased by the hungry internal parasites, yet the rapid growth of these robbers maintains the general plumpness of a healthy larva. But the ichneumons, having at last devoured the store of fat, and avoided the vital organs of the caterpillar, as if with a view to preserve their living home to the latest moment, now commence to attack the latter, speedily reducing the vitality of their host to the lowest ebb, and finally causing its death.
This untimely end may come before the caterpillar is full grown, or the insect may change to the pupa before the ichneumons have done their worst, but it rarely occurs that the unfortunate creature has sufficient strength to carry it on to the final stage.