Ranidae 



to the shoulder. The hind feet are fully webbed. (Figs. 281 

 and 282.) 



The colour varies greatly, not only according to the sex, 

 but also among individuals of the same sex. The Bullfrog 

 has power to change colour considerably. The general colour 

 of the upper parts is dull olive-green, marked with irregular, 

 dusky spots of brown. However, when the frog is in warm air, 

 and exposed to bright light, the skin may become a beautiful 

 spotless yellow-green, very light in tone. The Bullfrog just 

 from the mud, or from some place of concealment in deep water, 

 is so dark-coloured that he is nearly black. Experiments prove 

 that light has much to do with these changes of colour; at least, 

 that these changes in colour take place with changes of light, 

 when temperature and moisture conditions remain the same.' 



The female is usually more brown and spotted, and the 

 male more nearly plain green. The under parts of both are 

 white, with distinct or indistinct mottlings of brown. The 

 male has a bright yellow throat; that of the female is dirty 

 white, mottled with brown. The ear of the male is much larger 

 than that of the female. 



This description holds regarding the Bullfrog of north- 

 eastern North America. In southern New York, and still 

 farther south, the Bullfrog is more likely to be spotted, and 

 the male lacks the bright yellow on the throat. The Bullfrog 

 of Texas has the underparts vividly marked everywhere with 

 irregular, connected black spots. This frog of the Southwest 

 has also a more tubercular and leathery skin. There are prob- 

 ably three or four distinct varieties of this species in different 

 localities of North America. It is certain that the Bullfrog 

 of Wisconsin and adjoining regions is different enough to be 

 classified as a variety. (Fig. 278.) It is finely spotted with 

 dark on all parts except the head. There is much more bright 

 yellow in its colouration than in that of Bullfrogs from other parts 

 of North America. The male has this colour not only on the 

 throat, as in the case of the Eastern Bullfrog, but also along 

 the sides of the body and on the legs and feet to the tips of the 

 toes. The head is relatively more pointed than that of other 

 Bullfrogs. The body is relatively longer; the head is contained 



1 See pp. 22 to 27 for discussion of change of colour in the Batrachia. 



230 



