154 THE STORY OF REPTILE LIFE. 



Tie bites with great energy at a struggling grass- 

 hopper, and while thus exercising himself the blue 

 fades out from his body altogether, and his whole 

 body takes the colour of the brown earth on which 

 he stands. After tarrying a minute or two he ran 

 up the other tree, and the dull light blue colour 

 seemed to return to him." Since the female of 

 this species is similarly coloured, it may be that 

 this naturally variable coloration has been in- 

 creased by sexual selection. 



Equally vivid are the changes displayed by the 

 red Agama. 



Agama sanguinolenta. Dr G-adow, on the 

 authority of a German naturalist, Zandes, thus 

 describes the many changes of colour displayed 

 by this lizard : " The usual garb is earthy brown 

 above, with somewhat darker and indistinct 

 markings. The under parts are whitish. Some- 

 times the creature changes to dirty white, at 

 other times into blackish or grey brown. Bluish- 

 red stripes may appear on the sides of the body ; 

 blue lines begin to show on the throat, and 

 alternately the whole belly, originally white, 

 may become ultramarine blue. When the general 

 tone happens to be sulphurous yellow, blue often 

 appears on the tail and limbs. Brick red appears 

 on four longitudinal rows of patches on the sides 

 of the body. Sometimes the whole animal assumes 

 .a vinous tinge, or it is at first greenish before 

 turning into blue. The change begins on the 

 tail and limbs, extends over the head, and at 

 length reaches the back. Eed appears in both 

 sexes, more frequently in the female ; blue almost 

 entirely in the male. Sunlight and warmth only 



