226 



ORTHOPTERA 



abbreviated, and on the whole is of subordinate importance to 

 the other three. These latter thus form four chief areas or fields, 

 viz. 1, mediastinal or marginal; 2, scapular or radial; 3, 

 median ; and 4, anal. These nervures and divisions may be 

 traced in a large number of existing and fossil Blattidae, but 

 there are forms existing at present which it is difficult to reduce 

 to the same plan. In JEuthyrhapha, found in the Pacific Islands, 



the hind wings are long and project 

 beyond the tegmina, and have a very 

 peculiar arrangement of the nervures ; 

 the species of Holocompsa also possess 

 abnormal alar organs, while the struc- 

 ture of these parts in Diaphana (Fig. 

 122) is so peculiar that Brunner 

 w^isely refrains from attempting to 

 homologise their nervures with those 

 of the more normal Blattidae. The 

 alar organs are frequently extremely 

 different in the two sexes of the same 

 n 1 o -T 7^- 1. ^ 7. -D -1 species of Blattidae, and the hind 



Fig. 122. Diaphanajieoen. Brazil. \ ^ ' 



A, The Insect, natural size ; B, wing may differ much from the teg- 



(IftrrYrunn^ekT''"''"'^''''^''^' '''^'^ ^' '^^^^^'^^ ^^^^'^^ ^^ departure 

 from the normal. So that it is not 



a matter for surprise that the nervures in different genera cannot 



be satisfactorily homologised. 



But the most peculiar wings in the family are the folded 



structures found in some forms of the groups Ectobiides and 



Oxyhaloides [Anaplectinae and Plectopterinae of de Saussure]. 



These have been studied by de Saussure,^ and in Fig. 123 we 



reproduce some of his sketches, from which it will be seen that in 



B and C the wing is divided by an unusual cross-joint into two 



parts, the apical portion being also longitudinally divided into 



two pieces a and h. Such a form of wing as is here shown has 



no exact parallel in any * of the other groups of Insects, though 



the earwigs and some of the Coleoptera make an approach to it. 



This structure permits a very perfect folding of the wing in 



repose. The peculiarities exhibited have been explained by de 



Saussure somewhat as follows. In the ordinary condition of 



Orthoptera the axillary or anal field (P) when the wings are 



An7i. Sci. Nat. Zool ser. 5, x. 1868, p. 161. 



