550 HYMEXOPTERA. 



Gall-insects, as already stated, are often destroyed by 

 little parasites belonging to the family CHALCIDID.E ; and 

 as these are liable to be mistaken for the former, especially 

 when coming from the same gall, it may be well to point 

 out the difference between them. The four-winged gall-flies 

 have rather long, straight, thread-like, and ascending anten- 

 nae ; the fore wings with a few veins, forming two triangular 

 meshes, one of which is very small, and situated near the 

 middle of the wing, the other mesh much larger, and near 

 the base ; the hind body roundish, but laterally compressed ; 

 and the piercer spiral or curved, and concealed. The Chal- 

 cidians have shorter, elbowed, and drooping antenna?, which 

 are enlarged towards the end ; a single vein, running from 

 the shoulder near the outer margin of the fore wing, uniting 

 with this margin near its middle, and emitting thence, to- 

 wards the disk of the wing, a short oblique branch, which 

 is enlarged or forked at the end ; the hind body generally 

 oval, pointed at the end in the females, and provided in this 

 sex with a straight piercer, which is more or less visible 

 beneath, and prominent at the extremity. By means of 

 their piercers, the Chalcidians thrust their eggs into the 

 galls made by various kinds of gall-insects, and the mag- 

 gots hatched from these eggs devour 

 the young of the gall-flies. (Fig. 254, 

 larva of a Chalcidian, which attacks 

 Cynips dichlocerus ; Fig. 255, pupa of 

 the same.) Nor do they destroy these 

 alone ; they prey upon many other 

 larva?, especially caterpillars, and also 

 on pupa3 or chrysalids. Some of them are egg-parasites, 

 puncturing the eggs of other insects, and depositing therein 

 their own tiny eggs. They are the minute ichneumons 

 (IchneumoneB minuti) of Linnaeus, and, like the true ich- 

 neumon-flies, they are eminently useful in checking the 

 increase of the noxious tribes. 



Such being the known habits and services of the greater 



, 



