The Insect referred to by Trimen is, we believe, the _Batrachotettix whiti_ of de Saussure. In this species the alar organs are completely absent, and the pronotum forms a sort of hood that protects the base of the hind body. Some of the desert Eremobiens vary so much that the differences found among individuals of the same species {306}are said by Brunner and de Saussure to be so great as to affect even the generic characters, and give rise to the idea of an "uncompleted species-formation." [Illustration: FIG. 186.—Portions of middle of the body and hind leg of _Methone anderssoni_ ♂: _a_, femur; _b_, an inferior fold; _c_, rattling-plate; _d_, striated surface; _e_, the adjoining sculpture; _f_, grooved portion of tegmen. The part _e_ is really, like _d_, a portion of the second abdominal segment, not of the third, as might be supposed from the figure.] _Methone anderssoni_, an inhabitant of the Karoo Desert of South Africa, is one of the largest of the Acridiidae. A female of this species is represented of the natural size in Fig. 185. This Insect is remarkable on account of the complex organs for producing sound, and for the great modification of the posterior legs (Fig. 185, _b_), which do not possess locomotive functions, but serve as a portion of the sound-producing apparatus, and as organs for protecting the sides of the body. This Insect is said to be very efficient in making a noise. The sexes differ considerably in their sound-producing organs, a portion of which are present in the female as well as in the male (Fig. 186). Connected with the first abdominal segment, but extending backwards on the second, there is a peculiar swelling bearing two or three strongly raised chitinous folds (Fig. 186, _c_). When the leg is rotated these folds are struck by some peg-like projections situate on the inner face of the base of the femur, and a considerable noise is thus produced. The pegs cannot be seen in our figure. This apparatus is equally well developed in female and male. On the second abdominal segment, immediately behind the creaking folds we have described, there is a prominent area, densely and finely striated (Fig. 186, _d_): this is rubbed by some fine asperities on the inner part of the femur near its base. Sound is produced by this friction on the striated surface, the sculpture of which is abruptly contrasted with that of the contiguous parts: these structures seem to be somewhat better developed in the male than they are in the female, and to be phonetic, at any rate in the former sex. {307}The male has the rudimentary tegmina (Fig. 186, _f_) much longer than they are in the female (Fig. 185), and their prolonged part is deeply grooved, so as to give rise to strong ridges, over which plays the edge of the denticulate and serrate femur. There is nothing to correspond to this in the female, and friction over the surface of this part of the male produces a different and louder sound. There can be little