550 
HYMENOPTERA. 
Gall-insects, as already stated, are often destroyed by 
little parasites belonging to the family Ciialcididje ; and 
as these are liable to be mistaken for the former, especially 
when coming from the same gall, it may be w'dll 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 Clial- 
cidians have shorter, elbowed, and drooping antennae, 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 
larvae, especially caterpillars, and also 
on pupae 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 
( Ichneu mows 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 
O D 
Fig 265. Fig. 256. 
