them which are richly endowed, and one would never imagine that they would have recourse to strangers in order to bring up their progeny. All their young family is usually entrusted to the care of a nurse, who lives just long enough to bring them up; she gives them convenient shelter under her roof, and often bestows upon them the last drop of her blood.
When the young one has at last abandoned her first resting-place, she begins to think seriously of Hymen; she changes her dress and her mode of life, and seeks no more extraneous assistance till she lays her eggs. Among the animals brought up in this manner, the most remarkable are the Ichneumons, which have always attracted the notice of entomologists. These charming creatures, whose shape is delicately slender, whose transparent wings flutter with so much grace, have a less stormy youth than their boldness would induce us to suppose. As the cuckoo lays her eggs in the nest of a strange bird, the mother ichneumon deposits hers in a caterpillar full of health, by means of a long and thread-like ovipositor, so that the larvæ as soon as they are hatched, find themselves in a bath of blood and viscera, which serves them for food. The different organs palpitate under the teeth of these intruders, and the young larva grows and increases in size till it is hatched under the skin of its nurse: this skin is the cradle of the ichneumon.
The young ichneumon devours its nurse piecemeal, organ after organ; and for fear that death should supervene too quickly, the mother takes care to chloroform the victim beforehand to make her last longer. The method which many of them adopt to get rid of their
young, reminds us forcibly of the turning-box in which they used formerly to place children whom they wished to be brought up by public charity; with this difference, that young ichneumons are not only fed and taken care of by some good neighbour, but that her body itself serves them as food.
It has sometimes happened that entomologists, instead of finding beautiful butterflies produced from the caterpillars which they had reared, have had nothing hatched but a brood of ichneumons. Was it not natural then for them to dream of the transformation of species, when they saw issuing from the skin of a caterpillar, which is usually transformed into a beautiful chrysalis, a swarm of small winged flies which disperse with the rapidity of lightning? These ichneumons discover with astonishing ingenuity the caterpillar which can bring up their young, and they often reach it with their ovipositor in the midst of a fruit, or in the substance of a branch of a tree. Every one knows the Anobium and other little beetles which attack wood, and live in the dark galleries which they excavate. The mother ichneumon knows perfectly how to discover the beetle which bores into our furniture, and winged ichneumons have often been seen to proceed from worm-eaten wood. It is not only caterpillars that are sought by ichneumons for the sake of their young; many kinds of larvæ of coleoptera and hemiptera, of aphides and weevils, are attacked by the mother ichneumons, which plunge their ovipositors between their articulations. These winged corsairs well know the weak points of their cuirass.
Ichneumons are therefore decidedly parasitical at this first period of their life. As they approach maturity, the
time of which varies more or less according to the species, each ichneumon takes his departure, seeks for booty on his own account, and passes through the last stages of his existence at full liberty in the open air. Nothing is more beautiful than this insect in the plenitude of its life. The species of the ichneumon are very numerous. Mons. Wesmael has devoted a part of his life to the study of these insects.
We often ask ourselves what can be the use of these little creatures—what good purpose can be effected by vermin which annoy everybody? Michelet replied to this question when he wrote “The Insect.” “Birds,” says the brilliant historian, “prefer to destroy those insects which are the most injurious.” We may say the same of those which we are now considering. The most common caterpillar, and that which is the most dreaded on account of its great fecundity, is precisely that which is more eagerly sought by the greater number of ichneumons. No less than thirty-five kinds of these little assassins fall on certain species, to make them serve as a quarry to be given to their young ones. The Bombyx pini is one of the most dangerous and destructive insects in our woods. The ichneumons would seem to take into consideration the too great fecundity of this moth, and instead of one species, as is often the case, thirty-five different species direct their attacks upon it. It would be indeed difficult for the mother to withdraw her young ones from the ovipositors of so many enemies, but there will be always enough of them remaining to keep up the balance in this little world; the greatness of the danger with respect to plants will be counterbalanced by the number of ichneumons which arrest the propagation of
the caterpillars. These insects contribute more effectually to the destruction of caterpillars than all the means employed by man. To arrest the Pyralis of the vine, its cultivators encourage the little Chalcis (Chalcis minuta); and it has lately been recommended to introduce the acarus which attacks the Phylloxera, in order to lessen the number of this new pest. Do not aphides also prevent the too rapid development of certain plants? and the black species which lives on Windsor beans has doubtless suggested to the gardener that he ought to cut off the head of the plant when the flowers appear.
Some other hymenoptera may be mentioned: for example, the Evaniadæ, the Chalcididæ, as well as the Tachinariæ, which are remarkable for this kind of life. At the moment when the mining hymenoptera introduce into their hiding-places the insects which they have seized, and which they destine for their young ones, the Tachinariæ introduce themselves by stealth, and lay their eggs on these provisions. Each kind of tachinariæ attaches itself to a particular insect. There is one essential difference between them and ichneumons, that the females of the latter perforate the skin of their victims with a pointed instrument, and cause their eggs to penetrate to the interior of the entrails; while the mother tachinæ, less cruel, are contented to lay their eggs on the surface of the skin, and leave to the larva the care of penetrating into the interior.