The ovaries in Stilopyga orientalis consist each of eight egg-tubes, placed at the periphery of a common receptacle or oviduct, the pair of receptacles themselves opening into a common chamber—the uterus—which is surrounded by a much branching serific or colleterial gland. In this chamber the egg-case is formed from the secretion of the gland just mentioned. According to Miall and Denny,[[152]] there is a spermatheca which opens not into the uterus but into the cloacal chamber behind it. Lowne doubts this diverticulum being a true spermatheca. The manner in which the eggs are fertilised and their capsule modelled is uncertain.[[153]]
Fig. 125.—Alimentary canal of Stilopyga orientalis. (After Dufour.) a, Head; b, salivary glands; c, salivary reservoir; d, crop; e, diverticula placed below proventriculus; f, stomach; g, small intestine; h, rectum; i, Malpighian tubes; k, extremity of hind body.
The internal reproductive organs of the male are very complex in Stilopyga orientalis; each testis consists of a number (30 to 40) of vesicles placed on a tube which is prolonged to form the vas deferens. There is a very peculiar large complex gland consisting of longer and shorter utricles, opening into the vesiculae seminales, and forming a "mushroom-shaped gland."[[154]] This gland is much larger than the testes proper, which, it is said, lose early their functional activity in the species in question, and shrivel. There is another important accessory gland, the conglobate gland of Miall and Denny, opening on a portion of the external copulatory armour.
Although some species of Blattidae are domesticated in our houses, and their bodies have been dissected by a generation of anatomists, very little is known as to their life histories. The common "black beetle" of the kitchen is said by Cornelius to be several years in attaining the adult state. Observations made at Cambridge by the writer, as well as others now being carried on there by Mr. H. H. Brindley, quite confirm this view, the extent of growth accomplished in several months being surprisingly little, and the amount of food consumed very small. It is therefore not improbable that the life of an individual of this species may extend to five years. Phyllodromia germanica, a species that is abundant in the dwellings of the peoples of north-eastern Europe, attains its full development in the course of a few months.
We have already alluded to the fact that in the Blattidae the eggs are laid in a capsule formed in the interior of the mother-Insect. This capsule is a horny case varying much in size and somewhat less in form in the different species; it is borne about for some time by the mother, who may not infrequently be seen running about with it protruding from the hinder part of the body. Sooner or later the capsule is deposited in a suitable situation, and the young cockroaches emerge; it is said that they are sometimes liberated by the aid of the mother. Mr. Brindley has found it very difficult to procure the hatching of the young from their capsules.
Fig. 126.—Egg-capsules of European Blattidae. A, Ectobia lapponica; B, Phyllodromia germanica; C, Heterogamia aegyptiaca. (After Brunner.)
It is known that some Blattidae are viviparous. In the case of one such species, Panchlora viridis, it appears probable that the egg-capsule is either wanting, or is present in only a very imperfect form.[[155]]
On emerging the young Blatta is in general form very similar to the parent, though usually much paler in colour. After casting the skin an uncertain number of times—not less than five, probably as many as seven—it reaches the adult condition, the changes of outer form that it undergoes being of a gradual nature, except that at the last ecdysis the wings—in the case of the winged species—make their appearance, and the terminal segments of the body undergo a greater change of form. What mutations of shape may be undergone by the thoracic segments previous to the final production of the wings has not apparently been accurately recorded, Fischer's opinion being evidently based on very slight observation. The little that has been recorded as to the post-embryonic development since the observations of Hummel[[156]] and Cornelius[[157]] will be found in the works of Brunner.[[158]] According to this latter authority, in the wingless species the terminal segments of the body have the same form in the early stages as they have in the adult state, so that this latter condition can only be recognised by the greater hardness of the integument. When tegmina or wings are present in a well-developed form in a Blattid, it is certain that the Insect is adult; and when there can be seen at the side of the mesonotum or metanotum a piece, however small, separated by a distinct suture, it may be correctly assumed that the individual is an adult of a species having only rudimentary alar organs. The adult female of the common Stilopyga orientalis shows this phenomenon.