The Tetrapoda: Amphibia, Reptiles, Birds 599 



sylvatica. All of these have life cycles similar to that of R. pipiens al- 

 though the bullfrog spends two or three years as a tadpole. 



In the spring of the year, the high-pitched calls of the spring 

 peeper, Hyla crucijer, and the cricket frog, Acris gryllus, are heard from 

 every meadow pond or stream side. These are members of the family 

 Hylidae which are distinguished by their possession of suction discs 

 on the ends of their toes. Most members of this family, however, are 

 tree frogs and use these adhesive discs in climbing. 



The true toads are all members of the family Bufonidae, and can 

 be separated from the frogs by their warty skin and the parotid gland 

 behind the eye. The toads are nocturnal in habit and feed voraciously 

 on insects. During the daytime, they hide under protective logs or 

 stones. The skin is provided with numerous glands which secrete an 

 irritating liquid. These secretions may be poisonous to would-be de- 

 vourers of toads, but are harmless when the animals are handled. Con- 

 trary to some beliefs, the skin of toads is not capable of causing warts. 

 Most of the toads are members of the genus Bujo and are fairly small 

 (about 3 inches long). One species, B. marinus, which ranges from 

 Texas south through Central and South America, may attain a length 

 of 10 inches. 



Although most members of this order have a life history similar to 

 that of R. pipiens, some show remarkable adaptations to unusual con- 

 ditions. Among many tropical forms, for example, there has been a 

 tendency to reduction of the larval stage. Thus in some, the larval 

 stage is passed in the egg and the miniature adult emerges. In 

 others, the eggs are retained in special pouches on the back of the fe- 

 male ; there development occurs, and again the larval stages pass very 

 rapidly. Examples of this condition are found in members of the family 

 Pipidae, Pipa pipa, the marsupial frog of northern South America, and 

 in Gastrotheca also of South America. During copulation, the eggs are 

 placed on the back of the female of Pipa pipa; here they develop in 

 special pouches. In Gastrotheca, the eggs are placed in a special skin 

 pouch in which development takes place. In Europe, the male obstetrical 

 frog, Alytes obstetricans, entwines the egg strings around his hind legs 

 and carries them about until they are ready to hatch. Another unusual de- 

 velopment is found in the spadefoot toad, Scaphiopus sp., of our south- 

 western states. This form lives in unusually dry areas and lays its 

 eggs in temporary ponds. The rate of development of the larvae varies 

 with the rate at which the pool dries in the spring. They may meta- 

 morphose into the adult form within a month's time. It has been 



