GEYLLIN^:. 219 



the stigma, by the prolongation of the third v. post-axillaris (fig. 9), or even by the 

 crossing of the two branches of the v. diagonalis (b) which form the speculum (fig. 21). 

 It is very variable, forming often one, two, or three cells, through its occasional 

 anastomosis with the margin of the speculum. 



The area apicalis (r) is unmodified, and does not belong to the tambourine. It is 

 formed by the apical branches of the v. media (m), the last three or four of which are 

 strongly curved inwards, the base of these branches being turned back by the speculum, 

 and the preceding two or three branches emerging from the v. involvens (i), the bases 

 themselves being confused with this vein. But in consequence of the variability of 

 the anastomoses and of the cells, the apical branches of the v. media seem sometimes 

 to belong to the extremity of the post-anal veins. 



Adventitious musical veins (vence obliques and vence transversa?). — The homologies 

 of all the normal veins as modified in the male elytra are thus explained, but there 

 are still in the tambourine of the males other musical veins («), occupying the large 

 discoidal cell, between the v. diagonalis and the v. media. These nervures are to solidify 

 this cell, and, besides emerging directly from the v. stridulans, they receive probably 

 special vibrations. They afford useful characters to the systematist by their number, 

 direction, and form, and are characteristic of the tribes and through the tribes of the 

 genera, as will be shown below. They are of two different types : — 



(a) Vence obliques, sensu stricto. — These nervures exist in variable number, extending 

 more or less obliquely from the vena stridulans to the v. media ; the posterior (inner) 

 one anastomoses sometimes at its base by an arch with the v. diagonalis (fig. 9, v) ; 

 often they anastomose all together at their base by such arches, and are united to the 

 v. stridulans by adventitious reticulation. In addition, there are often at the outer 

 angle of the v. stridulans or v. analis (a) a few very short, rudimentary, false oblique 

 veins (Tab. XII. fig. 14), which may be taken as the homologues of the transverse 

 venulse of the normal reticulation, and which do not belong to the drum. But the 

 limit between them and the real oblique veins cannot well be defined. 



(b) Venw transversce. — These are never more than two in number, and they are found 

 only in a few genera of the group Eneopterinae, and give to the tambourine a very 

 typical character. In this type the vence obliques, as described, do not really exist, 

 except a rudiment of the last one forming the arch which unites it to the base of the 

 diagonal vein (figg. 22, 23). They are replaced by two transverse veins (v), which are 

 anastomosed with the base of the single rudimentary oblique vein. 



The true oblique veins I consider to be purely adventitious. There is nothing 

 homologous to them in the elytra of the females. They (fig. 9, v.) appear to be 

 formed by foldings of the membrane of the large ulnar cell. Indeed, in some 

 species, the membrane of the large cells becomes striated or somewhat folded, 

 showing a tendency to form adventitious nervures (fig. 29). The form, direction, 



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