590 NETJROPTERA. 



The genus Psocus, which closely resembles in its appear- 

 ance and habits the Aphides, though the species are not suck- 

 ing insects, has three ocelli, two or three-jointed tarsi, and well 

 developed wings. The species are very numerous, and abound 

 during the close of summer. Psocus venosus Burin, is said by 

 Fitch to live on the maple, while P. salicis he describes as 

 being found on the willow. . 



PERLIDJE Leach. This group comprises those Neuroptera 

 with long flattened bodies, the sides of which are parallel, while 

 the prothorax is large ; the antennae are long and thread-like, 

 and the wings are unequal in size, the posterior ones being 

 broad, triangular. The labial palpi are present, while the 

 mandibles exist ordinarily in a rudimentary state. The wings 

 are usually charged with many irregular transverse veins, and 

 w r hen folded flat on the back, extend beyond the abdomen. 

 The tarsi are three-jointed, and there are, in the typical genera, 

 two terminal setae on the abdomen. The pupae are active, with 

 prominent wing-pads. They are found in rivers under stones, 

 while the adults are found resting on leaves and in low damp 

 places. The larvae resemble the adult, except in being wing- 

 less, and tear a general resemblance to the larvae of certain 

 Ephemerids, showing the near relationship of the two families. 



The genus Pteronarcys is remarkable for retaining in the 

 adult state external gill-like filaments attached to the under 

 side of the prothorax. It consequently lives in exceedingly 

 moist places, much nearer the water than Perla. P. regcdis 

 Newman is fuscous, the head is no broader than the thorax, 

 while in P. proteus Newman the head is broader than the pro- 

 thorax and the abdomen is yellowish beneath. 



In Perla the wings are veiny, the transverse veins few and 

 very regular, while the hind wings have a large, plicated anal 

 space. The palpi are thread-like, and there are two abdominal 

 setae. Westwood remarks that "there is a very great diversity 

 in the sexes of the typical genus Perla, the males being much 

 smaller than the females, with very short wings." Perla ab- 

 normis Newman is yellowish fuscous, and the wings are sub- 

 hyaline with the veins clay-yellow. 



The genus Isopteryx is characterized by the wings having 



