Page:Jardine Naturalist's library Entomology.djvu/214

208 the inner edges approximate when closed, but the one usually overlaps the other. Although, for the most part semi-membranous, they vary considerably in consistency in different tribes. In certain species of Mantis, for example, they nearly assume the appearance of transparent reticulated wings, while among the convex-backed Blattæ they approach to the rigidity of elytra. They are generally reticulated by a series of strong nervures, radiating from the base to the summit, and crossed by a multitude of smaller ones, resembling fine lace. Sometimes, however, these nervures are visible only at the apex of the tegmina, but their existence is always obvious on the under side. Among the Grylli, the males of which are provided with a musical apparatus, situated at the base of the abdomen, some of the nervures are much more prominent than others, and instead of being longitudinal, are curved in a variety of ways; it is by rubbing these against the apparatus mentioned, that these insects produce the peculiar noise for which they are remarkable.

The under wings being adapted solely for flight, are of a much more delicate texture than the superior pair. They are traversed by a series of pretty strong parallel nervures, diverging from the base, and are folded up and expanded nearly in the same manner as a fan. From this cause they cannot be packed in so small a compass as in beetles, the wings of which are folded transversely upon themselves; accordingly, they are not always quite covered by the tegmina when at rest, and in some instances they