CHAPTER VIII 



INSECTS IN RELATION TO OTHER ANIMALS 



On the one hand, insects may derive their food from other animals, 

 either living or dead; on the other hand, insects themselves are food for 

 other animals, especially fishes and birds, against which they protect 

 themselves by various means, more or less effective. These topics form 

 the principal subject of the present chapter. 



Predaceous Insects. Innumerable aquatic insects feed largely or 

 entirely upon microscopic Protozoa, Rotifera, Entomostraca, etc.; this 

 is especially the case with culicid and chironomid larvae. Many aquatic 

 Hemiptera and Coleoptera prey upon planarians, nematodes, annelids, 

 molluscs and crustaceans ; Belostoma sometimes pierces the bodies of tad- 

 poles and small fishes ; Dytiscus also kills young fishes occasionally and is 

 distinctly carnivorous both as larva and imago. Among terrestrial 

 insects, Carabidae are notably predaceous, preying not only upon other 

 insects but also upon molluscs, myriopods, mites and spiders. Ants do 

 not hesitate to attack all kinds of animals; in the tropics the wandering 

 ants (Eeiton) attack lizards, rats and other vertebrates, and it is said that 

 even huge serpents, when in a torpid condition, are sometimes killed by 

 armies of these pugnacious insects. 



Mosquitoes affect not only mammals but also, though rarely, fishes 

 and turtles. The gadflies (Tabanidae) torment horses -and cattle by 

 their punctures; and the black-flies, or buffalo gnats (Simulium), per- 

 secute horses, mules, cattle, fowls, and frequently become unendurable 

 even to man. The notorious tsetse fly (Glossina morsitans) of South 

 Africa spreads a deadly disease among horses, cattle and dogs, by inocu- 

 lating them with a protozoan blood-parasite, to the effects of which, 

 fortunately, man is not susceptible. 



Parasitic Insects. Insects belonging to several diverse orders have 

 become peculiarly modified to exist as parasites either upon or within the 

 bodies of birds or mammals. 



Almost all birds are infested by Mallophaga, or bird lice, of which 

 Kellogg has catalogued 264 species from 257 species of North American 

 birds. Sometimes a species of Mallophaga is restricted to a single 

 species of bird, though in the majority of cases this is not so. Several 



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