24 THE BIOLOGY OF THE FROG chap. 



when a frog is started up it almost invariably makes a jump 

 for the water. In this way the creature has a ready mode of 

 escaping, not only from man, but from a number of other 

 enemies which might easily overtake it in a fair field. After 

 its first plunge into the water the frog usually swims some 

 distance under the surface and then comes up, exposing 

 only the tip of its snout above the water to get air. Fre- 

 quently, if there is grass or weeds near the water's edge, the 

 frog will swim a few strokes away from the shore and then 

 turn back and quietly come to the surface among the vege- 

 tation, where its advent would usually not be suspected by 

 the observer. 



During the breeding season in the spring, frogs are more 

 closely confined to the water than at other times of the year. 

 In the summer they wander farther from the water in search 

 of food. Different species vary greatly, however, in this 

 respect. The wood frog, Rana sylvatica, is commonly 

 found in woods miles away from any pond or stream. Most of 

 the other North American species of Rana are more closely 

 confined to an aquatic habitat. In Europe the water frog, 

 R. esculenta, is decidedly aquatic in its habits, whereas other 

 species, commonly spoken of as the grass frogs, scatter 

 through the meadows and woodlands after the breeding 

 season. 



Food. — The food of frogs consists of earthworms, in- 

 sects, spiders ; in fact, of almost any kind of animal small 

 enough to be seized and swallowed. Large frogs have no 

 sentimental scruples against devouring their smaller relatives. 

 The large bullfrog is an especially dangerous enemy to other 

 members of its genus. I have often found the stomach of 

 this animal greatly distended from its having swallowed 

 nearly full-grown specimens of Rana pipiens. Earthworms 

 are a favorite article of diet ; a hungry frog will devour sev- 



