II HABITS AND NATURAL HISTORY OF THE FROG .39 



bers of their own class. The large Cryptobranchus devours 

 frogs, and even toads. I have several times found large 

 bullfrogs with Rana pipiens in their stomachs, and it fre- 

 quendy happens that small individuals fall victims to larger 

 members of their own species. 



Among the invertebrates there are few species that 

 actively prey upon the frog if we exclude those forms which 

 are parasitic. Many aquatic bugs, such as Belostoma, Bena- 

 cus, Zaitha, Ranatra, and even the small back-swimmers, 

 Notonecta, catch the young tadpoles and suck out their 

 blood. Water beetles, such as Dytiscus, and the stealthy 

 larvae of the dragon flies make use of the same source of 

 food. Mortality among the tadpoles is naturally high, as 

 they are preyed upon by many forms which are unable to 

 cope with the adult frog. Water fowl, fishes, and aquatic 

 insects prevent the great majority from reaching maturity ; 

 and the young frog is exposed to many dangers from which 

 older and larger individuals are exempt. It is very proba- 

 ble that but a small part of the favored few who reach 

 maturity and perpetuate their kind die of old age. The 

 stomach of some larger animal forms the inevitable destina- 

 tion of all but a small per cent of the product of any 

 brood. 



The crayfish is often found devouring the dead bodies of 

 frogs, and it is not improbable that occasionally it may cap- 

 ture an unwary specimen alive ; but, for the most part, it 

 probably makes use of frogs killed by some other means. 

 Certain species of Glossiphonia (Clepsine), among the leeches, 

 live upon frogs and turtles ; but they do not require a very 

 1-irge quantity of food, since one meal may suffice to keep 

 them alive for over a year. Like higher animals, frogs are 

 attacked by mosquitoes, but it is uncertain how much incon- 

 venience arises from this source. 



