STATES OF INSECTS. (Lgg.) 85 
use their beaks for the purpose of depositing their eggs 
in different vegetable substances, and perhaps principally 
in fruit or grain. ‘The tribe of gall-flies (Cynzps) on 
the contrary, whose economy, detailed in a former let- 
ter*, interested you so much, bore an opening for the 
ege with their spiral oviduct, which also conveys it. 
Another large tribe of insects depositing their eggs 
singly, are those which feed upon the bodies of other 
animals, into the flesh of which they are either inserted, 
or placed so as speedily to find their way into it. Some 
of these introduce them into living animals, and then 
leave them to their fate, as the Jchneumons and gad-flies: 
others deposit them along with the dead body of an in- 
sect interred in a hole, often prepared with great labour, 
as the different species of sand-wasps (Sphecid@), spider- 
wasps (Pompilide), &c.: the manners of the latter of 
these tribes have been already adverted to”; and those 
of the Ichneumonidae, &c. will come more fully under 
consideration when I treat of the diseases of insects. 
A similar labour in providing suitable habitations for 
their eggs is undergone by various other insects whose 
larvee live chiefly on vegetable food, some inserting their 
egg within the substance the larva devours, as those that 
prey on timber, twigs, roots, or the like ; and others on 
its surface. One would suppose at first, that the exceed- 
ingly small egg which produces the subcutaneous larvee 
would, by the parent moth, be imbedded in the substance 
of the leaf which is to exhibit hereafter their serpentine 
galleries: but this is not the case, for she merely glues it 
on the outside; at least such was the situation of the only 
@ Vo. I. p. 446—. b Vox, L. p. 345—. 
