216 DISEASES OF INSECTS. 
each of which forty or fifty minute Ichneumons emerged. 
Aninsect also of this Order, that is a great benefactor to 
mankind, as a destroyer of the plant-lice,—I mean the la- 
dy-bird (Coccinella), in its larva state is itself subject to the 
attack, as we learn from De Geer, of one of these small 
parasites*. He detected them also in that of two species 
of weevils (Curculio L.): and in the pupa of some large 
grub of a beetle inhabiting the wood of the elm, perhaps 
that of the stag-beetle, he found the pupa of one of those 
Ichneumons that have an exserted ovipositor®. Doubt- 
less, did we know their history, we should find that num- 
berless species have their internal assailants belonging to 
this tribe. 
Orthopterous larvee seem not to have been yet an- 
nounced as affording a pabulum to these animals: but 
the Jate Dr. Arnold, whose tact for observation with re- 
gard to the manners and economy of insects has rendered 
his loss irreparable, discovered that the remarkable pa- 
rasitic genus Evania F. was appropriated to the all- 
devouring Blatta. Whether it attacked it in its egg or 
larva state I have not been informed. This little bene- 
factor is here extremely rare, at least in the country; per- 
haps in towns, where the cock-roach abounds, it may be 
more common. 
The observations of naturalists have chiefly been con- 
fined to the Hemipterous genus Aphis; but these early 
attracted their notice. Leeuwenhoek has given a par- 
ticular and entertaining account of 
the proceedings of 
I. Aphidum L. As soon as the little flies approached 
their prey, they bent their abdomen, which is rather 
long, between their legs, so that the anus projected be- 
2 De Geer i. 583—. 11, 822— | 907. » Reaum, vi. 312, 
