REACTIONS OF THE HORNED LIZARD. 99 



the Sandia Mountains bordering on the upper side the very dif- 

 ferent Phrynosoma douglasii ornatissimum prevails. This species 

 is also found on the mesa but in much smaller numbers, and is 

 said by Bailey (I.e.} to occur in the Upper Sonoran Zone. The 

 whole region under consideration is given in his map as the 

 Upper Sonoran Zone, with the exception of the Sandia Mountains, 

 which include the Transition and Canadian Zones, in both of 

 w r hich the above variety of P. douglasii is found. Both mountains 

 and valley are considerably damper than the mesa, the former on 

 account of the greater annual rainfall, and the latter on account 

 of the proximity of the Rio Grande and the high water table 

 (10 cm. to 5 m. from the surface of the soil (Nelson, et al., '14)). 

 The distribution of these species seems to depend, not primarily 

 on air temperature or on the factors which define the Life Zones of 

 Merriam, although the upper limit of P. modestum approximately 

 coincides with the upper border of the Upper Sonoran Zone, but 

 upon factors which are in agreement in the river valley and the 

 mountain range. Ants, the principal natural food of P. modestum, 

 are more abundant in the mesa region, but this may be merely a 

 secondary factor as far as distribution is concerned, as the 

 animals eat and thrive well upon small beetles, plant bugs, grass- 

 hoppers, etc. The distribution of the species coincides with the 

 grassy step formation of Watson ('12) falling in Shelford's ('130) 

 third division, formations of savannas and grasslands. 



In captivity, it was observed that the lizards ate readily any 

 living and moving insect or other animal of sufficiently small 

 size. The animals have been observed even to ingest lead shot 

 kept in motion by being rolled down an inclined plane, and 

 occasionally snap at moving sand grains. The attempts of a 

 medium-sized P. douglasii to swallow an earthworm of three 

 times its own length were rather interesting. The lizard braced 

 itself by means of its legs and attempted to pull the worm apart, 

 but finally succeeded in swallowing it whole, shaking it in the 

 process much after the manner of a dog shaking a snake. Large 

 woolly caterpillars, grasshoppers of considerable size and other 

 seemingly difficult objects were swallowed with comparative 

 ease. The animals were never observed in the act of drinking 

 and evidently obtained the amount of moisture required with 

 the food. 



