THE WINGS OF SALTATORIAL ORTHOPTERA 131 



The tracheation of the musical organs. — In the males of the Locustidae 

 (Fig. 122) and of the Gryllidae (Fig. 125) the formation of a musical organ 

 has been attained by a modification of the cubital and anal areas of the 

 front wings. An extreme case of this is furnished by the male of Oecanthus 

 (Fig. 125). The principal vibrating area of the wing lies between the 

 branches of the cubitus, which diverge widely in this sex. 



Although the wings of the two sexes of Oecanthus present a very different 

 appearance, there is really a ver^^ close correspondence in the tracheation, 

 and consequently in the venation, of the two, as can be seen by comparing 

 the lettering of Figures 124 and 125. 



The anal furrov/. — A study of the musical organs of adult Orthoptera 

 throws light on the nature of the anal furrow. In the female this furrow 

 lies between the cubitus and the first anal \'ein; but in the males of the 

 Locustidae and Gryllidse the anal furrow crosses bcin Cu2. It is evident, 

 therefore, that this furrow is merely a fold in the adult wing, and that its 

 position is variable. It will be shown later that in the Heteroptera, when 

 an anal furrow is developed, it is in front of the cubitus, instead of in the 

 more tisual position between the cubitus and the first anal vein. 



The venation of the wings. — It does not seem worth while to give a 

 detailed discussion of the venation of the wings, as the data given above 

 regarding the tracheation of the wings of nymphs furnish material for 

 determining the homologies of the wing-veins of adults. There are, how- 

 ever, some features of the venation of the wings that merit attention. 



The cross-veins. — Although well-developed cross-veins are present in the 

 wings of the Orthoptera, it is an interesting fact that in a considerable part 

 of the wings the spaces between the principal veins are traversed by an 

 in-egular network of veins resembling those of the more generalized Palaeo- 

 dictyoptera. In this respect the Orthoptera (including the Blattidae) is 

 the most generalized of the orders of recent insects. 



The venation of the anal area of the hind wings. — In many of the salta- 

 torial Orthoptera the anal area of the hind wings bears a striking resem- 

 blance to the wings of the Ephemerida, there being a regular alternation of 

 convex and concave veins. In these cases the concave veins are evidently 

 a later development than the convex veins. The increase in the number of 

 the branches of the anal tracheee takes place at the caudal end of the series, 

 and about each added trachea a convex vein is developed. It is only after 

 the space between two of the convex veins becomes wide enough to admit 

 of a fold in the wing that a concave vein is developed, and this development 

 takes place in the same manner as in the Ephemerida; the convex veins 

 being of the accessory type, and the concave veins, of the intercalary type. 



In some cases, as in the hind wings of Scudderia (Fig. 123), a tertiary 

 set of anal veins is developed; these extend only a short distance from the 

 margin of the wing, and increase the resemblance of this area to an 

 ephcmerid wing. 



