REPTILIAN LIVERIES 173 



each side of the saddle-shaped markings, and another on 

 each side of the body. These stripes rapidly become very 

 distinct, and at the same time the saddles begin to fade, 

 so that in the adult form, which is assumed during the 

 fourth year, the coloration is of a uniform yellow or 

 brown, traversed by four longitudinal stripes. 



In an earlier chapter, when discussing the coloration of 

 young birds, mention was made of one or two cases wherein 

 the young developed bright colours which were wanting in 

 the adult stage ; but among birds it is rare to find the 

 young brighter than the adults, as is the case, for example, 

 with several species of warblers in their immature con- 

 dition. Among the lizards, on the contrary, there are 

 many such instances, from which we select one or two of 

 the more striking. Thus, in the American blue-tailed 

 skink {Eumeces quinquelineatus) the young have the tail 

 of a bright blue and the body blackish with five yellow 

 stripes. As it matures the tail fades to a sombre grey, the 

 body changes from black to brown, the stripes (in the 

 males at any rate) entirely disappear, and the head, in the 

 males, assumes a bright red hue. So strikingly different 

 are the two types of coloration that the adult was at one 

 time regarded as a distinct species. 



Among snakes there are several such instances. In 

 Wagler's viper, for example, a Malay species, the young is 

 of a bright grass-green, later on the scales develop black 

 edges. Gradually these increase their width, till in the 

 adult animal they have suffused over the whole scale, 

 transforming the sometime green livery into a black, or 

 nearly black one. In this particular case we seem to be 

 able to interpret the reason for the change. And this 

 because the creature is arboreal and feeds on birds. This 

 extremely agile prey it is able to capture with ease. 



