wing on top and use the file of this wing and the scraper of the left, just the reverse of the custom among the katydids.
Fig. 34. A mole cricket, Neocurtilla hexadactyla
The front wings of male crickets are usually very broad and have the outer edges turned down in a wide flap that folds over the sides of the body when the wings are closed. The wings of the females are simpler and usually smaller. The differences between the front wings in the male and the female of one of the tree crickets (Fig. 37) is shown at B and D of Figure 33. The inner half of the wing (or the rear half when the wing is extended) is very large in the male (D) and has only a few veins, which brace or stiffen the wide membranous vibratory area or tympanum. The inner basal part, or anal area, of the male wing is also larger than in the female and contains a prominent vein () which makes a sharp curve toward the edge of the wing. This vein has the stridulating file on its under surface. The veins in the wing of an adult female (B) are comparatively simple, and those of a young female (A) are more so. But the complicated venation of the male wing has been developed from the simple type of the female, which is that common to insects in general. The wing of a young male (C) is not so different from that of a young female (A) but that the corresponding veins can be identified, as shown by the lettering. Taking next the wing of the adult male (D), it is an easy matter to determine which veins have been distorted to produce the stridulating apparatus. When the tree crickets sing they elevate the wings above the back like two broad fans (Figs. 37, 40) and move them sidewise so that the file of the right rubs over the scraper of the left.
[57]
