158 INDIRECT BENEFITS DERIVED FROM INSECTS. 
tyrants of our lakes and pools — the all-devouring Libellulina’ The Asili 
also, which are always upon the chase, seize insects with their anterior 
legs and suck them with their haustellum, The cognate genus Dioctria, 
particularly D, @landica, prey upon Hymenoptera, by some unknown 
means, instantaneously killing the insect they seize. Many species also 
of Bmpis, whose haustellum resembles the beak of a bird, carry off in it 
Tipularie and other small Diptera; and, what is remarkable, you can 
seldom take these insects in coitu, but the female has a gnat, some fly, or 
sometimes a beetle, in her mouth. Can this be to deposit her eggs in, as 
soon as they are impregnated by the male? or is it designed for the nup- 
tial feast? Even Scatophaga stercoraria and scybalaria, and probably many 
others of the same tribe, feed upon small flies, though their proboscis does 
not seem so well adapted for animal as for vegetable food. 
The most unrelenting devourers of insects appear to be those belonging 
to my fourth division, which attack them under every form. These begin 
the work of destruction when they are larvae, and continue it during the 
whole of their existence. The earwig that haunts every close place in 
our gardens, and defiles whatever it enters, probably in some degree makes 
up for its ravages by diminishing the number of other insects. The 
cowardly and cruel Mantis, which runs away from an ant, will destroy in 
abundance helpless flies, using its anterior tibia, with which the thigh 
form a kind of forceps, to seize its prey. The water-scorpions (Nepa, — 
Ranatra, and Naucoris ), whose fore-legs are made like those of the Mantis, 
the water-boatman (Notonecta), which always swims upon its back, and 
Sigara, all live by rapine, and prey upon aquatic insects. Some of this 
tribe are so savage that they seem to love destruction for its own sake 
One ( Nepa cinerea), which was put into a basin of water with several 
young tadpoles, killed them all without attempting to eat one. 
~~ Those remarkable genera of the tribe of water-bugs (Hydrocorise 
Latr.), which glide over the surface of every pool with such rapidity, being 
gifted with the faculty of walking upon the water, Hydrometra, Velia, and 
Gerris, subsist also upon aquatic insects. A large number of the land- 
bugs (Geocorise Latr.), plunge their rostrum into the larvae of Lepidop- 
tera, and suck the contents of their bodies; and Reduvius personatus, 
‘which ought on that account to be encouraged, is particularly fond of the 
bed-bug, as, according to Kuhn, is Pentatoma bidens, six or eight of which, 
shut up in a room swarming with the bed-bug, for several weeks, com- 
pletely extirpated the latter.? 
\ But of all the insects that are locomotive and pursue their prey in 
) every state, none are greater enemies of their fellow tribes than the Libel 
| fulina, and none are provided with more powerful and singular instruments 
~ of assault. In the larvae and pupa states, during which they live in the 
water and prey upon aquatic insects, they are furnished with two pair of 
strong jaws, covered by a kind of mask armed with a pair of forceps or 
claws, which the animal has the power of pushing from it to catch any 
| thing at a distance.* When an aquatic insect passes within its reach, it 
\ 
1 Lesser, Z. i. 268. note. : 
2 Naturforscher, St. 6. and Fallen, Hemipt. Suec, 142, quoted by Westwood, Mod. 
Class. of Ins. ii. 486. 
5 Reaum, vi. 400. t. 86—88, 
