16 VENOMS 
‘ Nature,” write Dumeril and Bibron, ‘ seems to have caused 
the tints and colours of snakes to vary in accordance with their 
habits and modes of life. Generally speaking, the colours are 
greyish or dull in species that are wont to live among sand, or 
which bury themselves in loose earth, as also in those that lie 
in wait on the trunks or large boughs of trees; while these hues 
are of a bluish-green, resembling the tint of the leaves and young 
shoots of plants, in snakes that climb among bushes or balance 
themselves at the end of branches. It would be difficult to describe 
all the modifications revealed by a general study of the colours of 
their skins. Let us imagine all the effects of the decomposition of 
light, commencing with white and the purest black, and passing on 
to blue, yellow, and red; associating and mixing them together, 
and toning them down so as to produce all shades, such as those 
of green, of violet, with dull or brilliant tints more or less pro- 
nounced, and of iridescent or metallic reflections modified by spots, 
streaks, and straight, oblique, undulating, or transverse lines. Such 
is the range of colours to be found in the skin of snakes.” 
This skin is covered by a thick epidermis, which is periodically 
detached in its entirety, most frequently in a single piece. Before 
effecting its moult, the reptile remains in a state of complete repose 
for several weeks, as if asleep, and does not eat. Its scales grow 
darker and its skin becomes wrinkled. Then one day its epidermis 
tears at the angle of the lips. The animal thereupon wakes up, 
rubs itself among stones or branches, divests itself entirely of its 
covering as though it were emerging from a sheath, and proceeds 
forthwith in quest of food. 
The moult is repeated in this way three or four times every year. 
