262 DARWINISM 



CHAP. 



harmless Homalocranium semicinctum ; and Elaps lemniscatus 

 in Brazil is copied by Oxyrhopus trigeminus ; while in other 

 parts of South America similar cases of mimicry occiu", 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 -svith a hiss as if to strike a foe.^ 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 occui's in all examples of true mimicry.^ 



In the genus Elaps, alcove refeiTed 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 uj) 

 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 creatiu-e has probably acquired this structure and 

 habit because it frequents open or rocky districts Avhere 

 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 



^ Nature, vol. xxxiv. p. 547. 

 " Proceedings ofthcZool. Soc. of London, 1870, p. 369. 



