Proscopides in the form of the head and other characters. In most cases the sexes of the Proscopides differ from one another so strongly that it is difficult to recognise them as being of the same species. Usually both sexes are entirely apterous, but the Chilian genus _Astroma_ exhibits a remarkable exception and an almost unique condition of the alar organs, the mesonotum being in each sex entirely destitute of such appendages, while the female has on the metanotum rudiments of wings which are absent in the male. [Illustration: FIG. 179.—_Tettix bipunctatus._ Britain. A, The Insect magnified; B, part of the middle of the body; _a_, prolongation of pronotum; _b_, tegmen; _c_, wing.] The tribe Tettigides is a very extensive group of small Acridiidae, in which the pronotum extends backwards as a hood and covers the body, the tegmina and wings being more or less modified. In our British species (Fig. 179) this condition does not greatly modify the appearance of the Insect, but in many exotic species (Fig. 180) the hood assumes {301}remarkable developments, so that the Insects have no longer the appearance of Orthoptera. It would be impossible, without the aid of many figures, to give an idea of the variety of forms assumed by this prothoracic expansion. It is a repetition of what occurs in the Order Hemiptera, where the prothoracic hoods of the Membracides exhibit a similar, though even more extraordinary, series of monstrous forms. So great is the general similarity of the two groups that when the genus _Xerophyllum_ (Fig. 180, A) was for the first time described, it was treated by the describer as being a bug instead of a grasshopper. This genus includes several species from Africa. The curious _Cladonotus_ (Fig. 180, B) is a native of Ceylon, where it is said to live in sandy meadows, after the fashion of our indigenous species of _Tettix_ (Fig. 179). Very little is known as to the habits of these curious Tettigides, but it has been ascertained that some of the genus _Scelimena_ are amphibious, and do not hesitate to enter the water and swim about there; indeed it is said that they prefer plants growing under water as food. This habit has been observed both in Ceylon and the Himalayas. The species are said to have the hind legs provided with dilated foliaceous appendages useful for swimming. [Illustration: FIG. 180.—Tettigides: A, _Xerophyllum simile_ Fairm.; B, _Cladonotus humbertianus_. (After Bolivar.)] [Illustration: FIG. 181.—A, _Mastax_ (_Erianthus_) _guttatus_, male. Sumatra. (After Westwood.) B, profile; C, front of head.] The tribe Mastacides includes thirty or forty species of Acridiidae with short antennae and vertical head (Fig. 181, _Mastax guttatus_); they are apparently all rare and little {302}known, but are widely distributed in the tropics of the Old and New Worlds. Nothing whatever seems to be known of their habits or of their development.