158 INDIRECT BENEFITS DERIVED FROM INSECTS. 



tyrants of our lakes and pools the all-devouring Libellulina. 1 The Aslli 

 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. celandica, prey upon Hymenoptera, by some unknown 

 means, instantaneously killing the insect they seize. Many species also 

 of Empis, whose haustellum resembles the beak of a bird, carry off in it 

 Tipularice 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 (Hydrocorisce 

 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 (GeoconscB 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. 2 



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- 

 lulina, 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. 3 When an aquatic insect passes within its reach, it 



1 Lesser, L. i. 263. note. 



2 Naturforscher, St. 6. and Fallen, Hemipt. Suec. 142. quoted by Westwood, Mod. 

 Class, of Ins. ii. 486. 



3 Keaum. vi. 400. t. 3638. 



