xxi INSECTA: NEUROPTERA 311 



venation recalls that of the Dragon-fly; the hinder wings, 

 however, are relatively small, a characteristic which serves 

 to distinguish them from the Perlidae, or Stone-flies, which 

 are next to be considered. 



Family 3 : PERLIDAE (THE STONE-FLIES) 



In the Stone-flies, the wings consist of a transparent mem- 

 brane with a network of nervures as in Dragon-flies and May- 

 flies, but the "nervures" are much stronger and more con- 

 spicuous ; also the hind wings are much larger, though not 

 longer, than the fore wings, and are broad at the base, all the 

 marginal part having a more complex venation than the rest 

 of the wing. The antennae in this family are long and flexible, 

 As in the two previous families, the larva is aquatic, and 

 the metamorphosis is gradual ; but the difference between 

 adult and larva is slight, except for the possession of wings 

 by the former. 



The Common Stone-fly (Perla bicaudata). 

 Perla bicaudata frequents river banks in June, seeming 



\ 





FIG. 232. The Common Stone-fly (Perla bicaudata). 

 (Natural size.) 



specially to favour rapidly flowing streams with stony beds. 



