FIELD BOOK OF PONDS AND STREAMS 



which there was such a ditch, and one of our charming pas- 

 times was that of capturing leeches and "putting them down " 

 each other's necks. Many of the family Glossiphonida (p. 

 154) are partial parasites, part of the time clinging to the thin 

 skin behind the legs of turtles and to the bodies of frogs and 

 salamanders, and part of the time foraging for snails and in- 

 sects over leaves and submerged trash. 



Food. — Most leeches will suck blood, if it is available, but 

 even the good blood-sucker, Macrobdella, feeds upon worms 

 and larvae in its youth. When fullgrown it lives mainly on 

 vertebrate blood, preferably human or cattle blood, but lack- 

 ing these it will satisfy itself with frogs, turtles, and tadpoles. 

 Some species feed upon worms and snails ; a few are cannibals, 

 and others are scavengers on dead animals. 



Associates. — No ver>^ definite information is available con- 

 cerning the enemies of leeches, but carnivorous fishes — trout, 

 sunfish, yellow perch, and black bass — are known to be im- 

 portant consumers, as well as various wading birds. 



Collecting, aquarium study. — Leeches are easily collected 

 and those from quiet water can be kept indefinitely in aquaria. 

 If they are found sticking to boards it is best to slide a knife 

 under them, then let them drop into the collecting dish. They 



Fig. 116. — Mouth regions of leeches showing: i, 

 the mouth which is but a small hole in the oral 

 sucker; 2, the large mouth occupying the whole 

 cavity of the sucker. 



152 



