262 
DARWINISM 
CHAl*. 
harmless Homalocranium semicinctum ; and Elaps lemniscatus 
in Brazil is copied by Oxyrhopus trigeminus; while in other 
parts of South America similar cases of mimicry occur, some¬ 
times two harmless species imitating the same poisonous 
snake. 
A few other instances of mimicry in this group have been 
recorded. There is in South Africa an egg-eating snake 
(Dasypeltis scaber), which has neither fangs nor teeth, yet it is 
very like the Berg adder (Clothos atropos), and when alarmed 
renders itself still more like by flattening out its head and 
darting forward with a hiss as if to strike a foe. 1 Dr. A. B. 
Meyer has also discovered that, while some species of the 
genus Callophis (belonging to the same family as the American 
Elaps) have large poison fangs, other species of the same genus 
have none ; and that one of the latter (C. gracilis) resembles 
a poisonous species (C. intestinalis) so closely, that only an 
exact comparison will discover the difference of colour and 
marking. A similar kind of resemblance is said to exist 
between another harmless snake, Megserophis flaviceps, and 
the poisonous Callophis bivirgatus; and in both these cases 
the harmless snake is less abundant than the poisonous one, 
as occurs in all examples of true mimicry. 2 
In the genus Elaps, above referred to, the very peculiar 
style of colour and marking is evidently a “ warning colour ” 
for the purpose of indicating to snake-eating birds and mam¬ 
mals that these species are poisonous ; and this throws light on 
the long-disputed question of the use of the rattle of the 
rattlesnake. This reptile is really both sluggish and timid, 
and is very easily captured by those who know its habits. If 
gently tapped on the head with a stick, it will coil itself up 
and lie still, only raising its tail and rattling. It may then 
be easily caught. This shows that the rattle is a warning to 
its enemies that it is dangerous to proceed to extremities ; 
and the creature has probably acquired this structure and 
habit because it frequents open or rocky districts where 
protective colour is needful to save it from being pounced 
upon by buzzards or other snake-eaters. Quite parallel 
in function is the expanded hood of the Indian cobra, a 
1 Nature, vol. xxxiv. p. 547. 
2 Proceedings of the Zool. Soc. of London, 1S70, p. 369. 
