WILD ANIMALS BENEFICIAL TO MAN 329 



Strawberries from the ravages of slugs and performing other 

 valuable offices of like nature. 



Beneficial Fishes (Pisces). — Much of the scavenging work 

 in the sea and fresh water is efficiently discharged by members of 

 this class. Among freshwater fishes Carp are particularly valuable 

 in maintaining the purity of our drinking supply, keeping it free 

 from insects, insect larvae, and decaying matter. They are not 

 infrequently kept in reservoirs on this account. And since the 

 larvae of such notorious pests as gnats, mosquitoes, and sand- 

 midges are all aquatic, we are largely saved from annoyance and 

 even from disease by the good offices of these and various other 

 freshwater fishes. 



Beneficial Insects (Insecta). — There are quite a large 

 number of insects which either when adult or in the larval state, 

 or it may be throughout life, are the natural enemies of many 

 notorious insect pests. Sufficient examples have already been 

 given in vol. ii, chap, ix, vol. iii, pp. 391-393, and in pp. 194, 195 

 of the present volume. 



Carrion is also largely destroyed by insect-larvae, such as the 

 grubs of Burying- Beetles and the maggots of various Flies. Nor 

 must we forget the large part which insects take in the fertilization 

 of plants (see p. 83), including many which are of great import- 

 ance to mankind. 



Beneficial Spider -like Animals (Arachnida). — Of the 

 members of this group it need only be said that Spiders, in par- 

 ticular, largely assist in keeping the numbers of insects within due 

 limits. 



Beneficial Myriapods (Myriapoda). — The numerous kinds of 

 Centipede undoubtedly destroy large numbers of noxious ground- 

 insects, and have therefore a claim to be included among beneficial 

 animals. 



Beneficial Crustaceans (Crustacea). — A large amount of 

 scavenging work is carried on by the members of this class, and, 

 so far as the sea is concerned. Crabs are particularly notable in 

 this respect. 



Beneficial Annelids (Annelida). — Earth-Worms render con- 

 siderable service to agriculture (see vol. ii, p. 258) in more than 

 one way. They reduce large quantities of soil to a finely-divided 

 state, making it into a suitable seed-bed, bring earth to the surface 

 as a sort of natural " top-dressing ", and it may be added that their 



