NATHAN BANKS. 21 



A REVIi!$IOIV OF THE BfEARCTIC HEMEROBIID^E. 



BY NATHAN BANKS. 

 (Plates III-V.) 



The Hemerobiidse are similar in general structure to the Chryso- 

 pidse ; however, they differ strikingly in several respects. They are 

 brownish in color, while the Chrysopidse are green ; they are much 

 less common than the latter family in specimens, yet the species are 

 as numerous; there is much greater dissimilarity among them in 

 structure and habits than among the Chrysopidse. None have been 

 observed to emit the disagreeable odor common to many Chrysopas. 



They differ structurally from the Chrysopidse in having a much 

 shorter pronotum, being broader than long, in having fewer cross- 

 veins in the wing, almost all represented in the two gradate series, 

 so that the cells are often four to six times as long as broad, while in 

 the Chrysopidse the cells are rarely more than twice as long as broad. 

 The latter family has always but one radial sector, which is connec- 

 ted back to the radius by at least six cross-veins, while in the He- 

 raerobiidte there are usually several radial sectors and when but one 

 it is connected back to the radius by not more than four cross-veins. 

 The difference upon which the family was based is that the antennae 

 are moniliform, that is, the joints are of nearly equal size through- 

 out; while in the Chrysopidse the antennae are setaceous, that is, the 

 joints taper toward the tip. Except one species, they are of smaller 

 size than the allied family. 



At rest the wings are held roof like over the body. Their flight 

 is slow, and often irregular I have never observed any flying in 

 bright sunshine (unless disturbed), however, at twilight or in cloudy 

 weather they become active, and at night are attracted to lights. 

 The adults have not been observed to take any nourishment, and 

 probably do not live more than a week or two, except during winter. 

 Several of the common species of Hemerobius evidently hibernate 

 in the adult condition, as the flies are taken in late fall and early 

 spring; others probably winter in the pupal condition. 



At least five of our Hemei'obiids occur also in Europe ; four of 



TRANS. AM. ENT. SOC. XXXII. DECEMBEE, 1905. 



