GKYLLIN^. 217 



Females (Tab. XIII. fig. 18). — On the dorsal field are : — <z, the medial vein (m), 

 next to the ridge, generally rather slender and furnishing at its extremity a few short 

 apical branches ; — 5, the ulnar vein (u), furnishing often three obliquely pectinated 

 branches ; — c, the anal vein, oblique ; — d, 2-3 axillary veins, terminating, like the 

 anal vein, on the inner margin (mar go suturalis) of the elytron. 



Males. — In some genera there does not exist a musical organ, and in this case the 

 male elytra do not differ from those of the females. 



But in most of the Gryllidae the musical organ is extremely well developed in the 

 males, and the elytra, except their apex and base, are converted into a tambourine. 

 The membrane is no longer rough, but transparent and parchment-like, not only on 

 the dorsal, but also on the lateral field. In the lateral field the nervures are the same 

 as in the females, but the vena mediastina bears a greater number of branches, and 

 these often take a sigmoidal curve. When the females possess a simple mediastinal 

 vein, the males of the same species have at least one (apical) branch. In the dorsal 

 field the nervures are so much deflexed that it is not possible to recognize them 

 except by a special study. 1 have given their nomenclature in a footnote on p. 216, 

 and will now endeavour to explain their homology. 



Homology. — All the longitudinal veins of the discoidal field, except the vena media, 

 instead of being straight, are angularly broken before the middle and deflexed 

 inwards nearly up to the sutural margin of the elytron. 



The vena analis (a, a!) forms thus a right or obtuse angle, and becomes more or less 

 transverse, to form the stridulating part (A), and then becomes longitudinal again (a'). 

 The other nervures follow the same direction. The transverse part of the v. analis (A) 

 is much thickened, prominent on the inferior side of the elytron, and is furnished with 

 rugosities like a file. It is by rubbing these rugosities against the inner edge of 

 the other elytron that the insect produces its musical sounds. This part of the anal 

 vein has been named by Goureau archet (bow) (plectrmn, Sss.)f. It is, indeed, 

 exactly like a fiddle-bow in its constitution and mode of action. As the right 

 elytron in the ordinary position covers the left elytron, it is generally the right which 

 produces the sounds by rubbing on the left one ; but the elytra can be indifferently 

 superposed at the will of the insect, and the left elytron sometimes rubs against 

 the right J. 



The three axillar veins (#, a/, a") run obliquely to the sutural margin. The first 

 two (#, a/) converge generally into a single short nerve, which is anastomosed with the 

 inner end of the vena stridulans (A) ; the fusion of these veins forms a corneous knot 

 (nodus analis) (n), which furnishes a solid support for the end of the vena stridulans 



* On fig. 9 the dotted line of the inferior z has been made too long, going through to the speculum. 

 f Vma stridulans, Brunner v. W. (in the Locustidse). 

 X Probably with the object of producing different sounds. 



biol. cente.-amee., Orthopt, February 1897. 2 Ff 



