The alar organs are difficult of comprehension, and different opinions prevail as to their morphology. The tegmina are extremely different to the hind wings, and never attain large dimensions, neither do they exhibit any leaf-like or ornamental structures. In the genus _Pteroplistus_ they are formed somewhat like the elytra of Coleoptera, and close over the back of the Insect in a fashion very like that found in beetles. According to Brunner the larger part of the tegmen—which, as we have said, reposes flat on the back of the Insect—represents merely the anal area, and all the other parts must be sought in the smaller, deflexed portion of the wing-cover. De Saussure's opinion, to a somewhat different effect, we have already mentioned. The tegmina of the male are extremely different from those of the female, so that it is a matter of much difficulty to decide what nervures correspond.[259] [Illustration: FIG. 205.—Tegmina (sinistral) of the house-cricket. A, male, inner aspect; B, female, outer aspect: _a_, inner margin; _b_, outer margin; _c_, nervure bearing stridulating file.] The wing-covers of the male differ from those of the Locustidae, inasmuch as the pair are of similar formation, each bearing a stridulating file on its lower aspect. This file projects somewhat inwards, so that its position is marked on the outer aspect of the wing-cover by a depression. Usually the right tegmen overlaps the other, an arrangement contrary to that which prevails in other Orthoptera. The wings are ample and delicate; they possess numerous nervures that are not much forked and have a {332}simple, somewhat fan-like arrangement; the little transverse nervules exhibit only slight variety. These wings are frequently rolled up at the apex, and project beyond the body like an additional pair of cerci (Fig. 204). The abdomen is chiefly remarkable for the large development of the pleura, the stigmata being consequently very conspicuous. The cerci are not jointed, though they are flexible and, often, very long; they bear a variety of sense-organs (Fig. 67). The saltatorial powers of the crickets are frequently considerable. Graber has observed the post-embryonic development of the field-cricket, _Gryllus campestris_, though unfortunately not from the very commencement, so that we do not know whether there are five, six, or seven ecdyses; the number is probably either six or seven. The manner in which the alar organs are developed is similar to that we have described and figured in the Locustidae. In the earlier instars there is a slight prolongation of each side of the meso- and meta-notum, but about the middle of the development a considerable change occurs—the rudimentary organs then become free appendages and assume a different position.