236 ENTOMOLOGY 



that have attained any degree of dominance among animals. Ichneu- 

 monidae, to be sure, are remarkably dominant among insects, but their 

 parasitic adaptations are limited for the most part to the larval stage, 

 and the adults may be said to be as free for new adaptations as are any 

 other Hymenoptera. 



Scavenger and Carrion Insects. Not a few families of Diptera 

 and Coleoptera derive their food from dead animal matter. The 

 aquatic families Dytiscidae and Gyrinidae are largely scavengers. 

 Among terrestrial forms, Silphidae feed on dead animals of all kinds; 

 the burying beetles (Necrophorus), working in pairs, undermine and 

 bury the bodies of birds, frogs and other small animals, and lay their 

 eggs in the carcasses; Histeridae and Staphylinidae are carrion beetles, 

 and Dermestidae attack dried animal matter of almost every description, 

 their depredations upon furs, feathers, museum specimens, etc., being 

 familiar to all. Ants are famous as scavengers, destroying decaying 

 organic matter in immense quantities, particularly in the tropics. 

 Many Scarabaeidae feed upon excrementitious matter, for example the 

 "tumble-bugs/ 7 which are frequently seen in pairs, laboriously rolling 

 along or burying a large ball of dung, which is to serve as food for the 

 larva. 



Insects as Food for Vertebrates.- Lizards, frogs, and toads are 

 insectivorous, especially toads. The American toad feeds chiefly upon 

 insects, which form 77 per cent, of its food for the season, the remainder 

 consisting of myriopods, spiders, Crustacea, molluscs and worms, accord- 

 ing to the observations of A. H. Kirkland, who states that Lepidoptera 

 form 28 per cent, of the total insect food, Coleoptera 2 7, Hymenoptera 

 19 and Orthoptera 3 per cent. The toad does not capture dead or 

 motionless insects but uses its extensile sticky tongue to lick in moving 

 insects or other prey, which it captures with surprising speed and preci- 

 sion. In the cities one often sees many toads under an arc-light engaged 

 in catching insects that fall anywhere near them. Though its diet is 

 varied and somewhat indiscriminate, the toad consumes such a large 

 proportion of noxious insects, such as May beetles and cutworms, that 

 it is unquestionably of service to man. 



Moles are entirely insectivorous and destroy large numbers of white 

 grubs and caterpillars; field mice and prairie squirrels eat many insects, 

 especially grasshoppers, and the skunk revels in these insects, though it 

 eats beetles frequently, as does also the raccoon, which is to some extent 

 insectivorous. Monkeys are omnivorous but devour many kinds of 

 insects. 



