226 DISEASES OF INSECTS. 



Ichneumonidan devourers. These in some cases are so 

 numerous as to destroy the tithe of the kinds they at- 

 tack 1 . Thus an ever- watchful PROVIDENCE prevents 

 these parasites from becoming so numerous as to anni- 

 hilate in any place the species necessary for the mainte- 

 nance of the general economy and proportion of animal 

 and vegetable productions. Amongst the assailants of 

 the Hymenopterct) none seem to have a more laborious 

 task assigned them than those that pierce the various 

 galls in which the larvae of the Cynips tribe are inclosed. 

 To look at an oak-apple, we should think it a work of 

 difficulty, requiring much sagacity and address, for one 

 of our little flies to discover the several chambers lurk- 

 ing in its womb, and to direct their ovipositor -> each 

 of them. Its CREATOR, however, has enabled it instinc- 

 tively to discover this, and furnished it with an appro- 

 priate 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 an egg. 

 When it prepares to perforate the gall, the Ichneumon 

 begins by depressing this organ, that it may extricate it 

 from its sheath ; it next elevates its body as high as pos- 

 sible, and bending the instrument till it becomes per- 

 pendicular 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 5 . 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 

 Reaum. ii. 454 --. B De Geer ii. 879. 



