Fig. 209.—Tridactylus variegatus, France.
The exotic genus Rhipipteryx is allied to Tridactylus. It is widely distributed in South America, but the little Insects that compose it are rare in collections, their saltatorial powers no doubt making it difficult to catch them; little is known as to their habits. In the undescribed Amazonian species we figure (Fig. 210), the wings, instead of being mere rudiments, as in Tridactylus, are elongate and project beyond the body; they are of a blue-black colour, and arranged so as to look as if they were the abdomen of the Insect; they, moreover, have a transverse pallid mark, giving rise to an appearance of division. It is difficult to form any surmise as to the nature of so curious a modification of the wings.
The Tridactylides have no tympana on the legs, and their affinity with the Gryllidae is very doubtful. Dufour thought T. variegatus to be more allied to the Acridiidae. He based this opinion chiefly on some points of the internal anatomy, but pointed out that Tridactylus differs from the Acridiidae in having no air-sacs in the body.
Fig. 210.—Rhipipteryx sp., Amazon valley.
Not many of the Gryllidae are so peculiar as the forms we have mentioned. The family consists in larger part of Insects more or less similar to the common cricket, though exhibiting a great variety of external form. The common cricket of our houses, Gryllus (Acheta) domesticus (Fig. 204), has a very wide distribution in the Old World, and is also found in North America. It is believed to have had its natural distribution extended by commerce, though really nothing is known as to its original habitat. The shrill chirping of this little Insect is frequently heard at night in houses, even in the most densely inhabited parts of great cities. Neither the female nor the young are musical, yet the chirping may be heard at all seasons of the year, as young and adults coexist independent of season. The predilection of Gryllus domesticus for the habitations of man is very curious. The Insect is occasionally found out of doors in the neighbourhood of dwelling-houses in hot weather, but it does not appear that this species leads anywhere a truly wild life. It is fond of heat; though it rarely multiplies in dwelling-houses to any great extent, it is sometimes found in profusion in bake-houses. Usually the wings in the cricket are elongate, and project backwards from under the tegmina like an additional pair of cerci; a variety, however, occurs in which these tails are absent, owing to abbreviation of the wings.
There is no beauty in the appearance of any of the Gryllidae, though many of them are very bizarre in shape. Very few of them venture to leave the surface of the earth to climb on plants. The species of Oecanthus, however, do so, and may be found sitting in flowers. They have a more Locustoid appearance than other Gryllidae. One of the most curious forms of the family is Platyblemmus, a genus of several species found in the Mediterranean region, the male of which has the head prolonged into a curious process (Fig. 211); this varies greatly in development in the males of the same species. It would seem that this organ is of a similar nature to the extraordinary structures we have figured in Locustidae (Fig. 189) and Mantidae (Fig. 136), though it appears impossible to treat the cephalic appendages of Platyblemmus as ornamental objects; their import is at present quite obscure.
A curious form of variation occurs in this family, and is called micropterism by de Saussure; we have already mentioned its occurrence in the house-cricket. The hind wings, which are usually ample, and frequently have their extremities rolled up and protruding like cerci, are sometimes much smaller in size, and not visible till the tegmina are expanded. De Saussure at one time supposed these micropterous individuals to be distinct species; it is now, however, known that intermediate examples can be found by examining a great many specimens. Some species are always micropterous.
Fig. 211.—Platyblemmus lusitanicus, male. A, front of head; B, profile of Insect with most of the appendages removed.