114 



Vniversity of Calif ornia PuUications. [Entomology 



ITT 



FIG. 52. Venation of a species of Blattidag from 

 Madagascar. Tlie front wings show a structure resem- 

 bling tiie Hemiptera. Arrows indicate lines of folding 

 in hind wing. 



The perfection of the folds is of more significance. The 

 nature of the folding may be seen in Figs. 52 and 53. Com- 

 paring these fig- 



nres, it will be seen 

 that the wing is 

 divided longitudin- 

 ally into an ante- 

 rior unfolded and 

 a posterior folded 

 area; that the 

 folded area is en- 

 tirely divided into 

 fields and entirely 

 concealed under 

 the anterior area ; 

 and further, that 

 each field embraces 

 a longitudinal vein 

 and an independ- 

 ent in front of it. Probably the first fold is the original one, 

 and the following folds represent wrinkles in the posterior area 

 separating tracts, each of which, after becoming successively 

 possessed of a longi- 

 tudinal vein and the 

 independent acces- 

 sory, became a defin- 

 ite flat field. Accord- 

 ing to this view, the 

 whole plicated area is 

 developed in adapta- 

 tion to the folds; in- 

 deed, the veins are 

 produced in the way 

 they are, in order to 

 perfect the folding of 

 this part of the wing. 

 In different members 



FIG. 53. Diagrams illustrating the folding of the 

 hind wing of a cockroach. Black areas are those 

 reversed in folding. Central figure shows folded 

 wing from beneath ; lower figure a cross-section of a 

 folded wing. 



of the family there 



may be a greater or less number of folds, and always a cor- 

 responding augmentation or diminution of the number of veins 

 in this region. 



