ix WARDING COLORATION AND MIMICRY 239 



of protection. Another exceptional case is- that of the very 

 conspicuous caterpillar of the spurge hawk-moth (Deilephila 

 euphorbia?), which was at once eaten by a lizard, although, as 

 it exposes itself on its food-plant in the daytime and is very 

 abundant in some localities, it must almost certainly be disliked 

 by birds or by some animals who would otherwise devour it. 

 If disturbed while feeding it is said to turn round with fury 

 and eject a quantity of green liquid, of an acid and disagree- 

 able smell similar to that of the spurge milk, only worse. 1 



These facts, and Mr. Poulton's evidence that some larvae 

 rejected by lizards at first will be eaten if the lizards are very 

 hungry, show that there are differences in the amount of the 

 distastefulness, and render it probable that if other food were 

 wanting many of these conspicuous insects would be eaten. 

 It is the abundance of the eatable kinds that gives value to 

 the inedibility of the smaller number ; and this is probably 

 the reason why so many insects rely on protective colouring 

 rather than on the acquisition of any kind of defensive 

 weapons. In the long run the powers of attack and defence 

 must balance each other. Hence we see that even the power- 

 ful stings of bees and wasps only protect them against some 

 enemies, since a tribe of birds, the bee -eaters, have been 

 developed which feed upon them, and some frogs and lizards 

 do so occasionally 



The preceding outline "will sufficiently explain the character- 

 istics of " warning coloration " and the end it serves in nature. 

 There are many other curious modifications of it, but these will 

 be best appreciated after we have discussed the remarkable 

 phenomenon of "mimicry,"' which is bound up with and 

 altogether depends upon "warning colour," and is in some 

 cases the chief indication we have of the possession of some 

 offensive weapon to secure the safety of the species imitated. 



Mimicry. 



This term has been given to a form of protective resem- 

 blance, in which one species so closely resembles another in 

 external form and colouring as to be mistaken for it, although 

 the two may not be really allied and often belong to distinct 



1 Stainton's Manual of Butterflies and Moths, vol. i. p. 93 ; E. B. 

 Poulton, Proceedings of the Zool. Soc. of London, 1887, pp. 191-274. 



