THE LIZARDS 147 



upper surfaces; the pattern consists of darker cross- 

 bands — sometimes of pale longitudinal bands on the 

 sides. The student will note such colors to be in har- 

 mony with the rocks and tree trunks on which these 

 creatures live. The chin and abdomen of the males are 

 decorated with glaring patches of blue or green, exhib- 

 iting varying degrees of intensity according to the ac- 

 tivity of the individual. 



Common in the deserts and sub-arid regions of the 

 Southwest is a large species known as Clark's Swift, 

 Sceloporus clarkii, often displaying a length of ten 

 inches. At times it is uniform, dull gray. Again, when 

 sporting in the sunshine, a curious transition of color 

 takes place. In the center of each scale a bright green 

 spot appears. Still this intensification of color does not 

 render the lizard conspicuous. Lying motionless on a 

 twisted stratification of rock it looks green from a short 

 distance away and might readily be mistaken for a thick 

 stem or a root projecting from some crevice. Let the 

 observer approach within, say fifteen feet, of the reptile, 

 and he will find he is intensely watched. With head 

 twisted slightly so that one of the sharp little eyes may 

 study every movement of the intruder, the lizard rears 

 the body slightly in preparation for a dash. One step 

 more on the invader's part and he is treated to a show 

 of agility almost too quick for the human eye to follow. 

 A gray streak whisks out of sight in an instant. Al- 

 most simultaneously, a scaly head is seen peeping around 

 a projection of the rock. It belongs to the same lizard, 

 now ready to engage in tactics that resemble hide-and- 

 seek if its capture is attempted. 



The largest and finest species of this genus is the 

 Collared Swift, S. torquatus, that so bristles with 

 coarsely-overlapping, spine-tipped scales it has also been 



