The tribe Pamphagides[236] includes some 200 species, found chiefly in Africa and the arid regions near the Mediterranean Sea. They are mostly apterous forms, and this circumstance has, according to de Saussure, exercised a marked influence on the geographical distribution of the species. Although the tribe consists chiefly of apterous forms, several species possess {304}well-developed wings; sometimes this is the case of the male but not of the female. Some of the species are highly modified for a desert life, and exhibit a great variation in the colour of the individuals in conformity with the tint of the soil they inhabit. _Xiphocera asina_ (Fig. 184) is thought by Péringuey to be the prey of the extraordinary South African tiger-beetles of the genus _Manticora_. We have already mentioned the tribe Oedipodides[237] as including most of the species of migratory locusts of the Old World. Some striking cases of variation in colour occur amongst the winged Oedipodides. In certain species the hind wings may be either blue or rosaceous in colour; it is thought that the latter is the tint natural in the species, and that it is due to the mixture of a red pigment with the pale blue colour of the wing; hence the blue-coloured wings are analogous to cases of albinism. But the most remarkable fact is that this colour difference is correlative with locality. Brunner von Wattenwyl says[238] that the blue variety of _Oe. variabilis_ occurs only in a few localities in Europe—he mentions Vienna and Sarepta,—and that where it occurs not a single red example can be met with. Similar phenomena occur in other species in both Europe and North America, and L. Bruner has suggested[239] that the phenomena in the latter country are correlative with climatic conditions. The group Eremobiens, a subdivision of Oedipodides, includes some of the most interesting forms of Acridiidae. Its members have several modes of stridulation. _Cuculligera flexuosa_ and other of the winged forms, according to Pantel,[240] produce sounds by the friction of the middle tibia against the wing, both of these parts being specially modified for the purpose in the male sex. The most peculiar members of the Eremobiens are some very large Insects, modified to an extraordinary extent for a sedentary life in deserts and arid places. Trimen says[241] that a South African species, _Trachypetra bufo_, which lives amongst stones, is so coloured that he had much difficulty in detecting it, and that he noticed in certain spots, often only a few square yards in extent, where the stones lying on the ground were darker, lighter, or more mottled than usual, that the individuals of the grasshopper were of a similar colour to the stones. {305}[Illustration: FIG. 185.—_Methone anderssoni_, female. S. Africa. _a_, Front of head; _b_, posterior leg; _c_, _d_, front and hind feet. (_c_ and _d_ magnified, the others natural size.)]