DISEASES OF INSECTS. 219 
the assailants of the Hymenoptera, none seem to have a 
more laborious task assigned them than those that pierce 
the various galls in which the larvee of the Cynips tribe 
are inclosed. To look at an oak-apple, we should think 
it a work of difficulty, requiring much sagacity and ad- 
dress, for one of our little flies to discover the several 
chambers lurking in its womb, and to direct their ovi- 
positor to each of them. Its Crearor, however, has 
enabled it instinctively to discover this, and furnished it 
with an appropriate elongated instrument, which will 
open a way to the deep and hidden cells in which the 
grubs reside, penetrate their bodies, and to each commit 
anege. When it prepares to perforate the gall, the Ich- 
neumon begins by depressing this organ, that it may ex- 
tricate it from its sheath; it next elevates its body as high 
as possible, and bending the instrument till it becomes 
perpendicular to the body and to the gall, so as to touch 
the latter with its point, it then gradually plunges it in, 
till it is quite buried*. A very remarkable Hymenopte- 
rous parasite (Leucospis), which when unemployed turns 
its ovipositor over the back of its abdomen, so that its 
end points to its head, is said to deposit its eggs in the 
nest of the mason-bee, most probably in the larva: but 
the curious observations that are stated to have been 
made by M. Amédée Lepelletier upon its history have 
not yet been given to the public®. 
Dipterous insects, likewise, do not escape from these 
pests of their Class: but few observations, however, have 
been recorded as to the species assailed by them. "We 
learn from De Geer, that a gnat (Cectdomyia Juniperi), 
4 De Geer. ii. 879—. & N. Dict. d Hist. Nat, xvii. 513. 
