356' NATURAL ARRANGEMENT OF INSECTS. 



the tibiffi are wanting ; and Phryganea itself exhibits 

 the largest species. 



(313.) Our next sub-family, the HemerohiincB, offer 

 less harmony of general structure, either in the per- 

 fect insect or the larva. These insects are usually 

 called lace-wing flies, from the elegant reticulation of 

 those organs, which are of comparatively considerably 

 larger dimensions ; and they differ from the last in 

 having the trophi free. They have rarely ocelli, and 

 their eyes have considerable metallic brilliancy : their 

 legs are short and slight, and their tarsi pentamerous. 

 Their larvae are not aquatic, but they are very ferocious 

 devourers of small insects ; this we have particularly 

 observed in that of Chrysopa perla ; and we have further 

 observed, in the transformations of this insect, that the 

 pupa creeps to some distance out of its cocoon when 

 ready to undergo its final change, aod then casts off 

 its pellucid skin, and emerges as the perfect insect. 

 Hemerobius has usually its wings covered with minute 

 hairs, and Osmylus has them beautifully spotted : the 

 latter is remarkable, also, for the possession of ocelli, — 

 a circumstance of rare occurrelice in this sub-family. 

 Although possessing large wings, they fly heavily, by 

 slo%vly flapping them, and their flights are very short. 

 They occur usually in hedges skirting brooks. Their 

 transformations approach closer to those of insects with , 

 a complete metamorphosis ; and there is less resemblance 

 between the larva and the imago, than in any of 

 the preceding sub-families, excepting only the last. It isfcf 

 in this same sub-family that we arrange Sialis and its 

 allies, Chauliodes and Corydalis : of these, the larva of 

 the first only has be,en observed, and which is aquatic ; 

 it is a common native. This larva is furnished with 

 branchise, as in the PhryganincB, and which aie arranged 

 somewhat similarly to those insects, — being attached to 

 the seven or eight first segments of the abdomen, but 

 ciliated ; it is gradually attenuated posteriorly, and has 

 a single caudal appendage ; and, like those insects, it 

 is probably carnivorous. Chauliodes and Corydalis are 



