IX 



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 (t) exists at the tip 

 of the wing just where the fold 

 takes place, so that when the 

 wing is shut this little piece is 

 liberated, as shown in t, Fig. 124. 

 In many Blattidae, e.g. Blabercu 

 (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 

 Thorax forcellana (Fig. 123, A) 

 and in Anaplecta azteca (123, B), 

 so that a, b of the latter may be 

 looked on as a greater develop- 

 ment of the condition shown in A 

 at t. It will be noticed that the 

 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 siljpka, 

 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 p 7 7 ^ 



Blatta folded, t, Free 0^6 ot Anaptecta, 



triangular area. (After The internal anatomv of Blattids has 



de Saussnre.) ,..,., * 



been investigated m only one or two species. 

 There are no great peculiarities, but some features of minor 

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

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



Fig. 123. Hind wings of Blattidae. A, 

 Thorax pcrrcellana ; B, Anaplecta 

 azteca; C, Dijoloptera silpha. (After 

 de Saiissure.) 



