DESTRUCTIVE ANIMALS 361 



sparrow has become a national pest, and should be exterminated 

 in order to save our native birds. It is feared in some quarters 

 that the English starling, which has recently been introduced into 

 this country, may in time prove a pest as formidable as the English 

 sparrow. 



Food of Herbivorous Animals. — We must not forget that other 

 animals besides insects and birds help to keep down the rapidly 

 growing weeds. Herbivorous animals the world over devour, 

 besides the grass which they eat, untold multitudes of weeds, which, 

 if unchecked, would drive out the useful occupants of the pastures, 

 the grasses and grains. 



Animals Destructive to Other Animals used as Food. — Directly 

 or indirectly, animals, either as parasites or not, in their struggle for 

 life, destroy quantities of food that man might use. Starfish are 

 enormously destructive to young clams and oysters, as the follow- 

 ing evidence, collected by Professor A. D. Mead, of Brown Uni- 

 versity, shows : A single starfish was confined in an aquarium with 

 fifty-six young clams. The largest clam was about the length of 

 one arm of the starfish, the smallest about ten millimeters in length. 

 In six days every clam in the aquarium was devoured. Hundreds 

 of thousands of dollars' damage is done annually to oysters in 

 Connecticut alone by the ravages of starfish. During the breed- 

 ing season of clams and oysters, the boats dredge up tons of 

 starfish which are thrown on shore to die or to be used as fertilizer. 



The liver fluke kills thousands of sheep every year. Tapeworms 

 in cattle and trichina in hogs spoil much available food. Round- 

 worms parasitize and kill, annually, very many food fish. 



Boring mollusks, such as the whelk, destroy multitudes of other 

 mollusks as food. Parasitic insects abound which kill useful 

 insects, some of which, like the honeybee, produce food. 



We can hardly estimate the harm done by one-celled parasites 

 and their carriers, the ticks, mites, etc., for they are enormously 

 destructive to cattle. 



Fish feed upon crustaceans and mollusks. The dogfish, shark, 

 and other elasmobranchs destroy many lobsters, crabs, and other 

 crustaceans, while many bottom-feeding fish eat mollusks. Fish 

 are cannibals also, eating eggs and young of their own kind. 

 Salmon eggs are a favorite bait of the western trout. Birds eat 



