CLASS AMPHIBIA 477 



their habits and therefore can be found during the daytime under 

 logs, in crevices or burrows in the earth, or in other situations where 

 they can protect themselves against this constant threat of desiccation. 

 Food and Feeding Habits. — Adult frogs and toads eat animal 

 food, while the tadpoles eat either animal or plant food. The food 

 of the adults consists primarily of living insects, worms, snails, 

 spiders and other small invertebrate animals. Many large frogs 

 and a few smaller ones are cannibalistic. Amphibians depend to 

 a large extent upon their sight in detecting food. While, in gen- 

 eral, frogs and toads will seize a moving object without much ex- 

 amination, the toads quite often stalk their prey and inspect it. 

 If a disagreeable insect, such as a stag beetle with strong mandibles, 

 is swallowed, it can be disgorged because, fortunately, the toad 

 has a wide esophagus. Most of the frogs and toads and many sala- 

 manders utilize their eyeballs in swallowing food. Their eyes can 

 be retracted into the head and by this action they help to push 

 food in the mouth cavity toward the esophagus. 



Amphibians can go for a long period of time without food. Tad- 

 poles may live for months, and experiments made on axolotls 

 (larvae of the tiger salamander) have demonstrated that they may 

 live for about a year on the food stored in their own tissues. Dur- 

 ing the hibernation season and breeding season most salamanders 

 and frogs do not feed. 



Enemies of Amphibia. — The enemies of amphibians are many. In 

 their larval or tadpole stages they are a delicate food for giant 

 water bugs, dragonfly nj^mphs, larvae of water beetles, and other 

 aquatic insects. Small crustaceans devour the gills of salamander 

 larvae, and fish appreciate their good flavor. Snakes, turtles, alli- 

 gators, birds, and mammals feed upon the adults and young. Man 

 enjoys the hind legs of frogs, and there is an increasing demand 

 for these as food. Man also destroys amphibians by polluting the 

 streams where they breed, and his automobile kills countless toads 

 and frogs on the highways. Nor are amphibians immune to disease 

 and gross infestation by parasites. 



Powers of Regeneration. — The power of regenerating lost parts 

 is one way in which Nature aids the group. Young tadpoles may 

 regrow limbs or tails, although adult frogs and toads are appar- 

 ently unable to regenerate lost appendages. The axolotl larva of 



