ICHNE UMON'-FLIES — GALL-FLIES 



189 



in other cases as gregarious parasites. At first the host appears but little injured, 

 hibernates, goes on feeding, and even enters the pupa-stage, so that at times the 

 pupa of the parasite may develop within the pupa of its host. Two-thirds of 

 the insects stung perish, however, before the pupa-stage is reached. Another 

 of the parasitic ichneumons is Basins sulcator, a species frequently found under 

 the bark on trunks of trees, where it hibernates. These flies are black, with the 

 middle of the abdomen red, and the legs reddish brown, the males having yellow 

 faces, and the females yellow mouths. 



Allied to the ichneumon-flies are the members of the family Braconidce, 

 characterised by their almost or entirely veinless wings. They comprise small 

 Hymenoptera, often not much more than one-tenth of an inch in length, many of 

 which are parasitic on beetles, while others, such as Microgaster nemorum, affect 

 Lepidoptera. This last-named species is black, shiny, and smooth, with pale reddish 

 yellow legs, and light - coloui-ed . 



hips ; it is one of the most im- 

 portant enemies of the pine-lappet 

 moth, depositing its eggs in the 

 caterpillar in the autumn. The 

 maggots proceeding from these 

 eggs hibernate with the half- 

 grown caterpillar, and in spring, 

 when fully grown, bore their way 

 out of the likewise full-grown 

 caterpillar, which they envelop 

 with their snow - white pupa- 

 coverings like a garment of fur. 



Next come the 

 Gall-Flies. 



gall - flies (Cyn 1- 



pida ), distinguished by their 

 sparsely veined wings (like the 

 Brni-uiri(hv), and straight, slender, 

 many-jointed antenna?, the small 

 compressed body, and the concealed ovipositor, 

 either in galls of their own production, or as so-called tenants of other galls. 

 The females lay in spring, mostly before the sprouting of the leaves, depositing 

 their eggs in various tender parts of the plants they affect, particularly those 

 of slow growth. Where the egg is placed a gall grows, the nature of which 

 depends, not only on the plant, but on the insect. The larva becomes a 

 pupa in the gall ; and some fifty kinds of galls are known on oak - trees 

 alone. In due course the pupa develops into the perfect insect, which gradually 

 eats its way out, to pass the winter beneath leaves in crevices of bark and such- 

 like shelters. On the lower side of oak-leaves are often found galls as large as 

 cherries — green, frequently red-cheeked, soft, juicy, and containing a larva in a 

 central cavity. The most common galls are produced by the oak gall-fly (Cynips 

 foil i ), which is a little over one-eighth of an inch long, and striped with red on the 

 back of the mesothorax, and brilliant black on the abdomen. The rose gall-fly 



OAK GALI.-FLT. 



Their larvae live on plants 



