The alar organs of the Mantidae are as regards the nervures and areas fairly similar to those of the Blattidae. The tegmina are usually narrow, and exhibit three well-marked areas; the one in front or external (according as the wing is expanded or closed) is the mediastinal area; it is usually more elongate and occupies a larger portion of the surface of the tegmen than in Blattidae. The middle area, forming the larger part of the wing, is occupied by the branches of the radial and ulnar nervures. The third area, the anal, possesses a sort of appendage in the form of a small space of a more delicately membranous nature at the inner part of the base. The tegmina are often more or less leaf-like in texture and consistence; this character is as a rule not very marked, but there are a few species with the tegmina very like foliage, this being more marked in the female; in some, if not in all, of these cases the mediastinal area is considerably increased. One tegmen overlaps the other, as in Blattidae, but to a less extent, and the correlative asymmetry is but slight: there is frequently a pallid spot close to the main vein on the principal area, nearer to the base than to the extremity. The hind wings are more ample than the front, and of much more delicate consistence; they possess numerous veins converging to the base; the anterior part of the wing is firmer in consistence, and its veins are more numerously furcate; there are many more or less distinct minute cross-veinlets, and an elegant tinting is not infrequent. They close in a fan-like manner, transverse folding being unknown in the family.
But little has been written on the internal anatomy of the Mantidae. Dufour has described only very partially that of M. religiosa. The salivary glands are largely developed, salivary receptacles exist; the alimentary canal possesses eight elongate coecal diverticula placed on the chylific ventricle; there are about one hundred Malphigian tubules. In each ovary there are about 40 egg-tubes, and they are joined at their bases in clusters of about half a dozen; each cluster has a common sinus; these sinuses are placed at intervals along a tube, which is one of two branches whose union forms the oviduct; there are a large number of "serific glands" of two kinds in the female. The testes are unusually complex in their structure.
According to Schindler[[172]] the Malphigian tubes in Mantis are not inserted, as usual, at the base of the intestine, but on the intestine itself at about one-third of its length from the base. There is some doubt about this observation. Schindler considers the fact, if it be such, unique.
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 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.
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.)
Dr. Pagenstecher has given an account[[173]] of the development of Mantis religiosa, from which it would appear that the statements of Fischer and others as to the number of moults are erroneous, owing to the earliest stages not having been observed. When the young Mantis emerges from the egg it bears little resemblance to the future Insect, but looks more like a tiny pupa; the front legs, that will afterwards become so remarkable, are short and not different from the others, and the head is in a curious mummy-like state, with the mouth-parts undeveloped and is inflexed on the breast: there are, he says, nine abdominal segments. The first ecdysis soon takes place and the creature is thereafter recognisable as a young Mantis. Pagenstecher's specimens at first would only eat Aphididae, but at a later stage of the development they devoured other Insects greedily: the number of ecdyses is seven or eight. The ocelli appear for the first time when the wing rudiments do so; the number of joints in the antennae increases at each moult. Dr. Pagenstecher considers that this Insect undergoes its chief metamorphosis immediately after leaving the egg, the earlier condition existing apparently to fit the Insect for escaping from the egg-case. In the immature stage of the Mantidae the alar organs appear (Fig. 139) as adjuncts of the sides of the meso- and meta-notum, projecting backwards and very deeply furrowed and ribbed in a wing-like manner. According to Pagenstecher, this wing-like appearance only commences in the fifth stadium, but he has not given particulars of the conditions of these parts in the preceding instars. According to de Saussure[[174]] the wings of the females of some species remain permanently in this undeveloped or nymphal state.
Fig. 139.—Tegmina (t) and wings (w) of immature Mantis.
