DISEASES OF INSECTS. 213 
eggs with her ovipositor repeatedly ; which in about fif- 
teen days were filled with the pupa, and in six more pro- 
duced the imago*. J. Ovulorum is the only known species 
of ego-devourers; but most likely there are many, vary- 
ing in size, according to the size of the ege they inhabit. 
Probably I. Atomus L., and I. Punctum Shaw, are of this 
description®. It is wonderful what a number these little 
flies destroy :—out of a mass of more than szxty eggs 
which was brought to De Geer, not one had escaped the 
Ichneumon*’. But the most extraordinary thing is, that 
even these little creatures we are told are destroyed by 
another still more minute‘. 
Though the animals we are speaking of usually de- 
stroy only a single egg, yet some appear not so to con- 
fine themselves. Geoffrey informs us that the larva of 
one of the _Ichneumons whose females are without wings 
(Cryptus F.) devours the eggs of the nests of spiders, and 
from its size—it is nearly a quarter of an inch long—it 
must require several of them to bring it to maturity °. One 
of those also which destroys the gnat infesting the wheat 
(I. inserens K.) appears to devour them in their egg state, 
and could not be brought to perfection by the food that 
a single one would furnish‘. 
The Ichneumons that are parasitic upon larve are 
the most numerous of all. Some of them are deposited 
by the parent fly on the outside of their prey, and others 
introduced into its interior. Ophion luteus F. is one of 
the former tribe; it plants its eggs in the skin of the ca- 
terpillar of the puss-moth (Cerura Vinula). Hach egg is 
* Reaum. vi. 296—. b Linne evidently has described 
another species under J. Ovwlorum, in F'n. Suec. 1644. 
© De Geer 1. 593—. d N. Dict. d Hist. Nat. vi. 10. 
© Geoftr. Hist. Ins. Par. ui. 361. * Lann. Trans. v. 102—. 
