14 



INSECTS INJURIOUS TO VEGETABLES 



Several kinds of birds, as also mammals, amphibians, and 

 reptiles, are well-known enemies of noxious insects, and domes- 

 tic fowls are of considerable value as destroyers of larvae, 

 especially such as are not hairy, like the "slugs" of asparagus 

 and potato beetles. 



Among beneficial birds, quail are important enemies of such 

 pests as the potato beetle and boll weevil. Mammals include 

 skunks, which kill great numbers of May beetles. Toads of 

 the amphibians are particularly useful as insect destroyers. 

 Chickens, ducks and turkeys 

 are all used in a practical way 

 by farmers for disposing of a 

 variety of insects. Turkeys ap- 

 pear to be naturally adapted as 

 substitutes for "hand-picking" 

 tomato or tobacco worms and are 

 actually employed and loaned 

 for such purposes, and swine 

 are equally fitted for the destruc- 

 tion of white grubs and other 

 subterranean pests. 

 The parasitic enemies of noxious insects are legion, but 

 their activity as useful allies to the farmer is to a large extent 

 dependent on atmospheric conditions. As a general rule also they 

 seldom appear in their greatest numbers until their injurious 

 hosts have done more or less damage. Their principal useful- 

 ness, then, is in so decimitating the numbers of noxious species 

 in one season that few are left to prey upon crops the following 

 year. 



The principal useful parasites belong to the family Hymenop- 

 tera, four-winged creatures of wasp-like appearance and variable 

 size. Of these are the ichneumon flies,^ chalcis flies,^ bra- 

 conids,' the egg parasites* and some others. 



1 Ichneumonidse. •'' Chalcidoidea. ^ Braconids. * Proctotrypidae. 



Fig. 21. — Pteromalus puparum. Male 

 Highly magnified. (Author's illustra- 

 tion, U. S. Dept. Agr.) 



