352 TROPICAL NATURE 



The universal avoidance by carnivorous animals of all 

 these specially protected groups, which are thus entirely free 

 from the constant persecution suffered by other creatures not 

 so protected, would evidently render it advantageous for 

 any of these latter which were subjected to extreme persecu- 

 tion to be mistaken for the former ; and for this purpose it 

 would be necessary that they should have the same colours, 

 form, and habits. Now, strange to say, wherever there is 

 a large group of directly-protected forms (division a of animals 

 with warning colours), there are sure to be found a few other- 

 wise defenceless creatures which resemble them externally so 

 as to be mistaken for them, and which thus gain protection, 

 as it were, on false pretences (division b of animals with 

 warning colours). This is what is called " mimicry," and it 

 has already been very fully treated of by Mr. Bates (its dis- 

 coverer), by myself, by Mr. Trimen, and others. Here it is 

 only necessary to state that the uneatable Danaidae and 

 Acraeidae are accompanied by a few species of other groups 

 of butterflies (Leptalidse, Papilios, Diademas, and Moths), 

 which are all really eatable, but which escape attack by their 

 close resemblance to some species of the uneatable groups 

 found in the same locality. In like manner there are a few 

 eatable beetles which exactly resemble species of uneatable 

 groups ; and others, which are soft, imitate those which are 

 uneatable through their hardness. For the same reason 

 wasps are imitated by moths, and ants by beetles ; and even 

 poisonous snakes are mimicked by harmless snakes, and 

 dangerous hawks by defenceless cuckoos. How these curious 

 Imitations have been brought about, and the laws which 

 govern them, have been already discussed. (See p. 54.) 



Sexual Colours 



The third class comprises all cases in which the colours of 

 the two sexes differ. This difference is very general, and 

 varies greatly in amount, from a slight divergence of tint up 

 to a radical change of coloration. Differences of this kind 

 are found among all classes of animals in which the sexes are 

 separated, but they are much more frequent in some groups 

 than in others. In mammalia, reptiles, and fishes, they are 



