162 3. IGUANID^ 



its colors again blend with those of the sand, making it 

 exceedingly difficult to discern, although one may have in 

 view the exact spot where it stopped. In such instances, 

 however, it often betrays itself by waving its tail above its 

 back like a plume, which then becomes a conspicuous object 

 owing to the contrast between the alternating black and 

 white bands. 



"I am unable to find any vegetable matter in the 

 stomachs of Tucson specimens. The contents of those ex- 

 amined apparently consist entirely of insects — beetles, grass- 

 hoppers, robber flies, and ants (a few) being distinguish- 

 able. From the stomach of one specimen. No. 618, a mass 

 of partially digested food was removed that may be veget- 

 able in its nature, but it is doubtful. 



"Several adult females taken in August contain large 

 eggs." 



Mr. Camp notes: "This lizard is abundant on the open 

 desert around the Turtle Mountains. It does not occur ort 

 the rocky hillsides, and even in the sandy canyon bottoms 

 is found but sparingly. It is on the open stretches of desert 

 dotted with creosote bushes that this species is typically at 

 home 5 and here it outnumbers all the other diurnal verte- 

 brates combined. Individuals may be observed bobbing up 

 and down, switching the tail from side to side, walking 

 jerkily along with the tail curled over the back, or running 

 with such speed that the eye can barely follow. The 

 writer estimated that one of these swift lizards covered a 

 distance of 90 feet in four seconds, which would be travel- 

 ing at a rate of about fifteen miles an hour. The lizards 

 can stop and start with the most confusing abruptness, and 

 rarely run straight away but describe a circle when pursued. 

 When tired out they may crouch close to the ground and 

 will then permit themselves to be caught; or they may 

 burrow into loose sand by wriggling the head from side to 



