It is certain that the plant-like appearance of some of the Locustidae renders them inconspicuous to the human eye in the situations they frequent. It is a matter of common observation that though the noise of their chirpings may be heard to such an extent as to make it certain that many individuals must be in the immediate neighbourhood, yet at the same time it may be most difficult to detect even a single individual. M. Boutan noticed this phenomenon in the case of Ephippigera rugosicollis, and tells us that the human eye can, with a little practice, acquire the art of detecting these concealed creatures. This consists apparently in making use, not of a general inspection, but of a scrutiny of the outlines of the leaves and twigs of a tree. By this means, when the eye is accustomed to the task, the Insects can be detected with comparative ease; much in the same way, M. Boutan says, as a figure, placed in an engraving in such a way as to elude the eye, is appreciated with ease after the eye has once perceived it.
Some of the Locustidae are provided with means of defence of a positive nature. The Algerian Eugaster guyoni ejects two jets of a caustic orange-coloured fluid from two pores situate on the sides of the mesosternum, and covered by the anterior coxae. This species is carnivorous as well as herbivorous, and produces a sound more like humming than stridulation.[[252]]
Fig. 200.—Phasmodes ranatriformis,female. Australia. (After Westwood.)
We have previously pointed out that some of the Acridiidae resemble the stick-Insects rather than the members of their own group; and similar cases occur amongst the Locustidae. Such a resemblance has, however, only been found in a few species of the tribe Prochilides. We figure one of these, Phasmodes ranatriformis, a native of South-West Australia. The very elongate linear form and the total absence of alar organs give this Insect a considerable resemblance to the stick-Insects or apterous Phasmidae. Prochilus australis is allied to this curious Locustid, but the alar organs are present in both sexes, and the Insect bears a great resemblance to the winged Phasmidae. This is due not only to the general form and colour, but also to the fact that the tegmina are very narrow, which causes them to look like the coloured slip on the anterior parts of the wings of some of the Phasmidae (cf. p. [266]). Another case of a Locustid with elongate, slender form is found in the extraordinary Peringueyella jocosa of South Africa, a member of the tribe Sagides. It has minute organs of flight, and reproduces, to a considerable extent, the form and appearance of Proscopides or of some Tryxalides.[[253]]
Fig. 201.—Schizodactylus monstrosus, male. Natural size. East India.
We follow Brunner in placing among the Locustidae the large Insect we represent in Fig. 201. It is remarkable on account of its tegmina and wings; these have their extremities much prolonged and curled; moreover, the flat interior area and the abruptly deflexed exterior area make them look more like the wings of Gryllidae. This species has no ocelli, and is said to be destitute of ears. The inflated condition of the anterior and middle tibiae suggest that it possesses auditory structures, though there appears to be no external opening for them. This Insect is found in India, where it is said to be common on the banks of sandy rivers, living there in burrows of the depth of three feet. Very little is known, however, as to this curious Insect. It has recently been reported[[254]] as being injurious to tobacco and other crops on high ground in Durbungha by cutting off their roots. The local name for the Insect is bherwa. We should think it somewhat doubtful whether this refers really to S. monstrosus.
Fig. 202.—Anostostoma australasiae, male. Australia.