1916 1 Camp: Amphibians and Reptiles .">11 



porus, and Dipsosaurus are known to part with their tails, the first 

 easily, the last with difficulty. In Sauromalus, Crotaphytus and 

 Phrynosoma autotomy does not occur. 



Notable in the case of many species, for example the desert horned- 

 toad, the gridiron-tailed lizard, the ocellated sand lizard, and the side- 

 winder, is the close resemblance between the color of the reptile as 

 viewed at a little distance and the color of its surroundings (see Atsatt, 

 1913, p. 49; Stejneger, 1890, pp. 114-115; and Yarrow, 1875, p. 512). 

 Color change in lizards may be seasonal, as in the orange-red nuptial 

 colors of female Uma, Callisaurus, and Crotaphytus wislizenii, tran- 

 sitory, as the colors exhibited by the long-tailed swift when under ex- 

 citement, or adaptive, as the dusky shades of gridiron-tailed lizards 

 and horned-toads when found on dark soil (see in this connection 

 Franklin, 1913, and Stejneger, 1890). 



The femoral pores in lizards secrete a substance which seems to be 

 of use during the breeding season. In many desert reptiles the period 

 of greatest sexual activity, from April to July, is accompanied in the 

 male by an abundance of the waxy secretion of these glands. Lizards 

 in which a decided difference was found at this time of year between 

 the size of the femoral pores in males and females were the chuckwalla, 

 the rough-scaled lizard, the gridiron-tailed lizard, the long-tailed swift, 

 the Bailey collared lizard, the ocellated sand lizard, and the desert 

 whip-tail. The pores function most actively therefore in adult males 

 during the early summer. 



The daily and seasonal habits of desert reptiles seem to show some 

 correlation with the distribution of the species. Those forms like 

 Dipsosaurus dorsalis, Uma notata, Sauromalus ater, Uta graciosa, and 

 Crotalus cerastes, which have ranges restricted to the hottest parts of 

 the desert, may be seen abroad at all hours of the day during the sum- 

 mer and scarcely ever appear in the winter. Uta stansburiana, which 

 is the only desert lizard ranging into the cooler Pacific coast district, is 

 the last to be driven into cover by the cool of winter and the first to 

 emerge on warm days. 



It is reasonably certain that most, if not all, of the American desert 

 reptiles do not require water. 



