270 



AMPHIBIA 



l"'iG. I44. Mid-wife toad, Alytes obstet- 

 rlciuis. (Courtesy of the Amer. Mus. of 

 Nat. Hist.) 



of the female protrude from her body and the eggs pass out to be 

 fertilized by the sperms and then are guided forwards so that they 

 are spread over the back of the female, where they sink into pockets 

 in the skin. Each pocket has a hinged lid which the larva lifts. 



Thej'?;-^ toad {Bomhuiator igneus) has a purplish ventral surface 

 with orange yellow patches. When alarmed it throws itself back 

 to display the brilliant abdomen, elevating the head and turning the 

 legs over the back. B. pachyphus, a poisonous variety, has lemon- 

 colored patches. 



The mid-wife toad {Alytres 

 obstetric ans) lives in France 

 and Switzerland. The eggs 

 are externally fertilized and 

 the male carries them away 

 with him into the water at 

 intervals. When they are 

 nearly ready to hatch, he re- 

 mains in the water to facili- 

 tate such development. 

 (Figure 144.) 



The spade-foot toad {Pelo- 

 bates cult7-ipes) is a toad which digs deep holes in the sand by 

 means of a spur on the hind foot. 



The Bufonidae, the true toads, comprise a large family which is 

 found on all continents of the globe. Toads possess a rough skin, 

 whose irregularities are caused by the large number of poison glands 

 contained in it. Their secretion is abundant and the toad is on this 

 account not attacked by many animals (see page 300). Bufo 

 leyitiginosiis americanus, the common toad of North America, is 

 considered to be of great economic importance. Estimates of its 

 value as a destroyer of injurious insects vary from ^5.00 to $15.00 

 per individual annually. Toads are said to devour plant-eating 

 millipeds which secrete hydrocyanic acid. (Figure 145.) 



The tree frogs ( Hylidae) are an extensive and widely distributed 

 family, there being over one hundred and fifty species. They have 

 the power of changing color from the ordinary green to either grey or 

 dark brown. By means of small discs on the tips of their toes they 

 are able to climb trees. They are extremely noisy at night when 

 they spend most of their time catching insects. One form (Noto- 

 tre?/ia) has in the female a fold of skin on the back serving as an egg 



