246 A BOOK OF INSECTS 



of insect is a fact so extraordinary that its meaning cannot 

 be mistaken. AVhatever power the birds of this vicinity 

 possessed as checks upon destructive irruptions of insect 

 life was being largely exerted here to restore the broken 

 balance of organic nature." 



It is well known that many English birds feed upon 

 insects. The titmice are especially useful, as they destroy 

 many crop pests in all their stages, and during the winter 

 clear off an enormous number of eggs and hibernating 

 insects. Swallows and martins capture myriads of flying 

 insects, including the large " daddy-longlegs ' or crane- 

 flies (Tipula). They have also been seen feeding upon 

 aphides at the time of their migration from the hop 

 gardens to their winter quarters on neighbouring plum 

 and damson trees. Nearly all the migrants, indeed, are 

 exclusively insectivorous. Among larger birds, the starling 

 and the green plover or lapwing wage a ceaseless war upon 

 many kinds of grubs and caterpillars which infest crops 

 and grass ; the kestrel, although the bulk of its food con- 

 sists of mice, consumes large numbers of beetles, especially 

 cockchafers ; while the latter insects, together with night- 

 flying moths, form the staple diet of the night-jar or 

 "fern-owl" — a very useful bird which, in the past, has 

 been subjected to much unwarrantable persecution by 

 ignorant, gun-carrying humanity. 



The food of adult fresh-water fishes has been investi- 

 gated in America by Dr. Forbes, who states that no less 

 than forty per cent, of the total supply is drawn from the 

 insect world. The principal insectivorous fishes are the 

 smaller species. The food of a little minnow (P/icnacobius), 

 for example, consists of insects to the extent of ninety- 

 eight per cent. — mostly the minute larvae of certain gnats 

 and midges. The latter are also consumed in enormous 

 numbers by many other fishes ; while the larvae of may- 



