1911] Bryant: Horned Lizards of California and Nevada 15 
Most of the species are found in a dry, sunny climate, and 
usually where there is sandy soil and very little vegetation. A 
well known exception is that of P. blainvillei frontale which 
oceurs in the forest belt of the Coast Range in California. Such 
an environment provides these lizards with an abundance of 
insect food,—ants, beetles, flies, ete. 
The horned lizard presents a fine example of protective 
resemblance. Wherever its home, it resembles the color of the 
substratum so closely that it is practically invisible except when 
in motion. Specimens from the white sand of the desert are 
very light in color, those from the black lava belt are almost 
black, whereas those from the vari-colored mountain districts 
show red and even bluish markings. How quickly a change 
in environment would bring about a change in color is not 
definitely known, although Coues (1875) states that the change 
takes place in from twenty-four to forty-eight hours. Several 
specimens of P. blainvillei blainvillei from Pasadena when kept 
in captivity on dark soil in the moister climate of Berkeley, on 
shedding their skin, showed a much darker color. This may 
have been due partly, however, to their being kept indoors, for 
Parker (1904) has proved that both light and temperature 
influence color change. 
The most distinctive thing about horned lizards is the circlet 
of horns which crowns the head. Any one who has seen a horned 
lizard on the defensive cannot doubt the value of these horns 
as a protection to the animal. With its head lowered so as to 
receive any blow on the horns and the large scales of the back 
elevated, it presents a very formidable appearance. In fact, 
the lizard seems to depend almost entirely on the ability to 
frighten its enemies, for aside from the horns it has no means 
of defense, as it seldom attempts to bite and is not a swift run- 
ner. As most of the species are represented by large numbers 
of individuals, the protection appears to have been adequate. 
The two greatest enemies of the horned lizard are the road 
runner (Geococcyx californicus) and the rattlesnake (Crotalus). 
A tradition existing among the Indians that a horned lizard is 
able to burrow its way out of a snake’s stomach seems to have 
some foundation in fact, for rattlesnakes have been found with 
