PHANEEOPTEEIN^E. 313 



an acute angle the end of the first post-axillary vein, forming with it an elongated 

 triangle, homologous with the angle formed posteriorly by the two axillary veins, in the 

 females, but not so much prolonged. 



This triangle is useless for the production of sounds ; it is only a homologue of the 

 normal veins of the female elytron ; it may be called the post-axillary triangle, its 

 margins being formed by the two post-axillary veins *. 



We have thus shown that the males of the Phaneropterinse have in the left elytron 

 a very powerful stridulating-organ, this being strongly coriaceous and supported by the 

 whole dorsal field. 



3rd. Bight elytron. — The veins are not so strongly deflexed as in the left elytron. The 

 first axillary vein is well separated from its base from the anal vein, and longitudinal, 

 as in the females, but frequently flexuous and much stronger ; it emits an obliquely 

 transverse stout branch, sometimes greatly thickened at the base. This nervure is the 

 homologue of the stridulating vein of the left elytron, but it is often divided into two 

 parallel branches, imitating the two transverse veins of the latter. Beneath, the first 

 axillary vein is not very prominent, showing that it is not a fiddle-bow, as in the left 

 elytron. Behind this transverse vein we find the post-axillary triangle, as in the left 

 elytron, but bordered with strong veins. — The second axillary vein is at the base 

 obliquely transverse (in the rest of the elytron appearing quite transverse, parallel to 

 the hind margin of the pronotum), and then becomes longitudinal and divides into two 

 parallel branches, which are much thickened and prominent and submarginal to the 

 sutural border, terminating in a sort of notch in the latter. The two thick branches 

 serve to consolidate the corneous margin, which forms the sonorous area (illex, comp. 

 antea, p. 218) on which the stridulating vein of the left elytron rubs to produce 

 the tunes, and they must be considered as the two strings of the fiddle. 



The post-axillary triangle is similar to that of the left elytron, but not quite 

 symmetrical with it ; its inner margin is formed by the second portion of the second 

 axillary vein, this being much thickened, broken off, and quite separated from the 

 first portion f . 



The tympanal field of the right elytron is thus divided into several compartments : — 

 1. At the base, the large axillary cell, generally convex, coriaceous and punctured, as 

 in the left elytron. 2. Outside, the elongate ano-axillary cell, partly membranaceous 

 and hyaline (outer speculum), except at the base. 3. The triangular (post-axillary) 

 area, also membranaceous (inner speculum). The second and third cells form the 

 tambourine of the elytron. 



At the posterior extremity of the triangle the veins become greatly reticulated, 



* Homologous with the first two post-axillary veins of Gryllidae. (Comp. anted, p. 217.) 

 t This anomaly is due to adaptation. The first part of the second axillary vein has become independent 

 to form the marginal strings, next to the ille.v, and thus the post-axillary triangle is separated from it. 



biol. cente.-amee., Orthopt., September 1897. 2 ss 



