Page:Jardine Naturalist's library Entomology.djvu/77

Rh different stages are four in number, that of egg, larva, pupa, and imago or perfect insect. All insects are, strictly speaking, oviparous. The few instances which might be supposed to prove that this is not universally the case, are more apparent than real deviations from the general law. Certain two-winged flies, cocci, ground-bugs, (Cimicidæ,) and aphides, give birth to larvæ; the forest-flies of the singular genus Hippobosca, and its near allies enter the world in the pupa state. The larvæ in question, however, are not developed in a uterus by means of a placenta, like the embryos of true viviparous animals, but come from eggs hatched within the body of the mother; while the forest-flies, besides being hatched in the same manner, likewise pass the penultimate stage of their life, which is probably of very short duration, in the matrix of the parent. These two tribes, therefore, may be said to be ovoviviparous. The eggs of insects do not often fall under our observation, on account of their small size, and being carefully concealed, by a variety of ingenious devices, that they may not fall a prey to birds and other enemies. Their most common situation, at least with such as produce herbivorous larvæ, is on the leaves designed to serve these larvæ as food; at other times they are placed in fissures of wood, made by an instrument specially designed for the purpose, and not unfrequently in fruits and grain; many are deposited in the earth, and not a few in water. They are placed either singly or in groups. Their defence