340 



BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Seasonal changes. — There are two seasonal pelages, winter and 

 summer, the latter worn only for a few weeks. The winter overhair 

 falls out at the beginning of hot weather, leaving the animal clad in 

 its winter underfur, which soon becomes brittle and worn, exposing 

 the dark color at base, when the animal looks ragged and' patchy, 

 often appearing to be blackish when seen at a distance. The summer 



Pig. 56.— Cynomys hiitovicianus aeizonensis. (Cat. No. 36362, U.K.N. M.) a, Dhrsai, view; 

 6, Ventral view; c, Latebal view. 



pelage is first acquired on the forefeet and head, extends slowly back- 

 ward over the shoulders,, but rapidly over the ventral surface and 

 inner sides of the hind limbs, then to their outer surface, and lastly 

 to the rump and tail. The underfur disappears at the advent of the 

 coarse summer coat,, in which it is wanting. The change from winter 

 to summer dress is a slow one, that from summer to winter much 



