WINGS OF COCKROACHES 



227 



closed collapses like a fan, and also doubles under the anterior 



part (H) of the wing along the line a a, in Fig. 123, A, the result 



being similar to that shown by our Fig. 124. It will be noticed 



in Fig. 123, A, that a small tri- 



angular area {f) exists at the tip 



of the wing just where the fold a " 



takes place, so that when the t 



wing is shut this little piece is 



liberated, as shown in t, Fig. 124. 



In many Blattidae, e.g. Blether a 



(Fig. 132), no trace of this little 



intercalated piece can be found, 



but in others it exists in various 



degrees of development interme- 

 diate between what is shown in g 



Thorax porcellana (Fig. 123, A) 



and in Anaplecta azteca (123, B), 



so that a, I of the latter may be 



looked on as e|, greater develop- 

 ment of the condition shown in A 



at t. It will be noticed that the q 



superadded part of the wing of 



123, B, possesses no venation, 



being traversed only by the line 



along which it folds ; but in 



the wing of Diploptera silpha, 

 123, C, the corresponding part 



is complexly venated. This venation, as Brunner says,^ is not 



an extension of the ordinary venation of the wing, but is sui 



generis. It is curious that though all the degrees of develop- 

 ment between A and B exist in various 

 forms of the tribes Ectobiides and Oxyha- 

 loides, yet there is nothing to connect the 

 veined apex of Diploptera with the unveined 



Fig. 124.— Hind wing of , Annnlecta 



BUtta folded, t, Free one Ot JLnapieClCl. 



triangular area. (After xhe internal anatomy of Blattids has 



de Saussure.) ^^^^ investigated in only one or two species. 



There are no great peculiarities, but some featiu'es of minor 



interest exist. The alimentary canal (Fig. 125) is remarkable 



1 Mouv. Syst. Blattaires, 1865, p. 265. 



Fig. 123. — Hind wings of Blattidae. A, 

 Thorax porcellcma ; B, Anaplecta 

 azteca ; C, Diploptera silpha. (After 

 de Saussure.) 



