The eggs of the Mantidae are deposited in a singular manner: the female, placing the extremity of the body against a twig or stone, emits some foam-like matter in which the eggs are contained. This substance dries and forms the ootheca; whilst attaining a sufficient consistence it is maintained in position by the extremity of the body and the tips of the elytra, and it is shaped and fashioned by these parts. The eggs are not, as might be supposed, distributed at random through the case, but are lodged in symmetrically-arranged chambers, though how these chambers come into existence by the aid of so simple a mode of construction does not appear. The capsule is hard; it quite conceals the eggs, which might very naturally be supposed to be efficiently protected by their covering: this does not, however, appear to be the case, as it is recorded that they are subject to the attacks of Hymenopterous parasites. The time that elapses after the eggs are laid and before they hatch varies greatly according to circumstances. In France, _Mantis religiosa_ deposits its eggs in September, but they do not hatch until the following June; while in E. India the young of another species of _Mantis_ emerge from the eggs about twenty days after these have been deposited. Trimen has recorded some particulars as to the formation of its egg-case by a _Mantis_ in S. Africa. This {247}specimen constructed four nests of eggs at intervals of about a fortnight, and Trimen states that the four were "as nearly as possible of the same size and of precisely similar shape." He also describes its mode of feeding, and says that it was fond of house-flies, and would eat "blue-bottles," i.e. _Musca vomitoria_, but if while eating one of the latter a house-fly were introduced, the "blue-bottle" was generally dropped, even though it might be in process of being devoured. The young have to escape from the chambers in which they are confined in these egg-cases; they do so in a most curious manner; not by the use of the feet, but by means of spines directed backwards on the cerci and legs, so that when the body is agitated advance is made in only one direction. The eggs last deposited are said to be the first to hatch. On reaching the exterior the young Mantids do not fall to the ground, but remain suspended, after the manner of spiders, to the ootheca by means of two threads attached to the extremities of the cerci; in this strange position they remain for some days until the first change of skin is effected, after which they commence the activity of their predatory life. [Illustration: FIG. 138.—Egg-case of _Mantis_ with young escaping: A, the case with young in their position of suspension; B, cerci magnified, showing the suspensory threads. (After Brongniart.)]