ORDER IV. PLECOPTERA. 



PERLID.*:. 



The stone-flies (Fig. 44, Nemoura) are also known 

 as Perlids. The body is long and flattened, with a 



large prothorax. The 

 antennae equal the 

 body in length. The 

 wings lie flat upon 

 the abdomen, con- 

 cealing it and extend- 

 ing some distance 

 beyond it. Their 

 plaited character 

 has given the name 

 Plecoptera (TrAeKos, 

 plaited ; Trrepov, a 

 wing) to the order. 

 The larva and pupa (Fig. 45) are aquatic, and 

 are often found under stones. They have external 

 gills on the under side of the thorax. 



The genus Pteronarcys lives in very wet places, 

 and this may account for the very exceptional fact 

 that the tracheal gills of the larva and pupa are re- 

 tained in the adult. 



The Plecoptera stand by themselves, but their lar- 

 vae present strong resemblances to those of the Ephe- 

 90 



Fig. 44. 



