36 



8REE0ING HABITS OF AMPHIBIA 



BANA SYLVATICA. the wood frog. Thia frog Is found only in the Northern States and Canada. 

 It rarely exceeds 2-5/U inches in body length, and Is light hrown in 

 color with a dark streak on either side of the head and a dark line 

 from the tip of the snout to the eye. There is also a black patch 

 over the tympanum. The dorsal plicae are prominent but not of a dif- 

 ferent color. The head is pointed. Its feeding habits are like 

 those of Bana piplena. 



These frogs breed in ponds, in wooded regions where there are 

 dead leaves and mud. They begin breeding in early March in water 

 at about 12°C. The eggs are larger than those of Rana pipiens 

 (about 2.0 mm.) and number about 5,000. Depending upon the tempera- 

 ture, metamorphosis is reached in from ko to 50 days. Development 

 is normal even at U°C., indicating wide temperature tolerance but at 

 a lower level than for Rana pipiens. Stage #12 to gill circulation 

 stage requires only about 95 hours at 15°C. and at 20°C. metamor- 

 phosis la achieved in it-5 days. 



.laiia sjlvatica, 

 tlie wood frog. 



(Courtesy C. H. Pope 

 l^kk: Chicago Mus. 

 Nat. Hist.) 



Exceptional cases of crosa-oviposition 



Noble and Aronson (19^2) report that when Rana clamitans or Rand sylvatlca males as- 

 sume the amplectlc position with ovulating Rana pipiens females, the grip is lateral and 

 below the axillae rather than ventral, as with pairs of Rana pipiens. This grasp seemed 

 to make it difficult for the female to oviposit and the caudal half of the male's body 

 tended to float away from the female. Even though the cloacae are not approximated (see 

 figure below) the eggs are not generally fertilized or. If fertilized, rarely develop be- 

 yond the gastrula stage in hybrid croasea ( aee aection on ^T-bridization) . 



Female Rana pipiens ovipositing witli male Rana 

 clamitans 



(Drawing made by the Illustrators Corps of 

 The American Museum of Natural History. 

 Loaned through courtesy of L. R. Aronson.) 



TOADS 



BUFO AMERICANUS , the American toad. This toad, common in gardens as a night prowler, is 

 found in the northeastern United States. The adults vary in size from 2 to U Inches in 

 body length, the males being smaller and possessing black china. The ventral surface of 

 these toads la aand colored and granular while the dorsal surface is warty. The eyes are 

 protruding £ind two large parotid glands extend backward from the eyes. The color is olive 

 green. Food consists primarily of large insects found around gardens. 



