The embryonic development of the mole-cricket has been studied by Dohrn[264] and Korotneff,[265] and is considered by the former to be of great interest. The tracheae connected with each stigma remain isolated, while, according to Korotneff, the development of the alimentary canal is not completed when the young mole-cricket is hatched. Perhaps it may be this condition of the digestive organs that necessitates the unusual care the mother bestows on her young. [Illustration: FIG. 208.—_Cylindrodes kochi._ Australia. A, outline of the Insect with five of the legs and the extremity of the body mutilated; B, middle leg. (After de Saussure.)] The genus _Cylindrodes_ (Fig. 208, _C. kochi_) comprises some curious and rare Insects of elongate, slender form. They are natives of Australia, where the first species known of the genus was found in Melville Island by Major Campbell, from whom we learn that these Insects burrow in the stems of plants, and are so destructive that he was unable to keep a single plant in his greenhouse on account of the ravages of _Cylindrodes campbellii_. The form of these Insects is beautifully adapted to {337}their habits, the body being contracted in the middle in such a way as to permit the middle and hind legs to be packed against it, so that the cylindrical form is not interfered with by these appendages while the excavating anterior legs are at work in front of the Insect. The abdomen has nine segments; the terminal one, said to be remarkably long and destitute of cerci, is not shown in our figure. The genus _Tridactylus_ is considered by de Saussure to form, with its ally _Rhipipteryx_, a division of Gryllotalpinae, but they are treated, perhaps more correctly, by Brunner as a separate tribe. _T. variegatus_ (Fig. 209) is a small Insect, abundant in sandy places on the banks of rivers in Southern Europe,—extending on the Rhone as far north as Geneva,—and is remarkable for its great power of leaping, and for the rapidity with which it can burrow in the sand. This anomalous Insect has only ten joints to the antennae. Its alar organs are imperfect, and not like those of other Gryllidae in either form or neuration. The hind legs are of peculiar structure, the tibiae terminating in two processes between which is situate a rudimentary tarsus. Near the extremity of the tibia there are some plates, forming two series, that can be adpressed to the tibia, or extended as shown in our figure. The body is terminated by four rather short, very mobile processes; the upper pair of these are each two-jointed, and are thought by de Saussure and Haase[266] to be cerci; the inferior pair, being articulated processes of the anal segment, their presence in addition to cerci is remarkable. It is difficult to distinguish the sexes of this Insect. [Illustration: FIG. 209.—_Tridactylus variegatus_, France.]