264 PREDACIOUS AND PARASITIC 



Such a larva is shown at Fig. 8 on Plate XIII., and, in its natural 

 situation on a stem or leaf, it often exhibits so little of the appear- 

 ance of an insect as to be taken, until a movement betrays it, for 

 a patch of dry lichen. Probably this habit may assist in protect- 

 ing it against the sharp eyes of birds. 



In some species of this sub-family the larvae are small and more 

 delicate in structure, rarely attaining to 5/i2ths of an inch in 

 length, and from their subdued grey colouring are much less 

 readily seen and captured than those previously described. They 

 are of exceeding quickness of movement, and complete their 

 larval existence in a shorter term than the young of the Chrysopi- 

 dcB. The pupa is but slightly covered with silk in those genera 

 which I have been able to observe, and the fly is as remarkable 

 for the dulness and soberness of its tints as that of the previously 

 described group is for its brilliancy. The wings of the Hemero- 

 biidce are generally thickly fringed with sparse, distinct hairs, 

 which arise also at the junction of the nervures of the wings. 

 The cross nervures of the latter are much fewer than in the 

 Chrysopidce^ and constitute an important differential character. 



The larva of Hemerobiidce is shown on Plate XIII. at P'ig. 3, 

 and the pupa at 9 and 9^. Fig. 4 shows the perfect insect which 

 emerged from the pupa, 9^. The disproportion between the size 

 of the pupa and the imago is not so marked in this sub-family as 

 in the ChrysopidcB, although even here it seems impossible that 

 the delicate wings should be contained in so small a space as that 

 occupied by the pupa. 



The most plentiful species of Hemerobiidce, so far as I am 

 aware, appears to be the H. humuhis^ which is found in great 

 numbers in hop gardens, where it performs an essential service to 

 man by the rapidity with which it destroys the fly — aphis humuli — 

 one of the great enemies of the hop-grower, and which is with 

 difficulty kept in check by artificial means. Some species, such as 

 that figured, frequent in the larval state fine grass, while others 

 may not uncommonly be taken beneath the leaves of the oak, on 

 the elder, and on the dog rose. 



Besides Hemerobiiis, two other genera of the sub-family are 

 believed to be aphidivorous : Drepanopteryx, a genus which con- 

 sists of one species only ; D. Fhalcenoides (Linn.), which is 



