168 ANIMAL COLORATION, 



until evening. I have a quantity of these caterpillars on some 

 thick-leaved shrubs in my garden ; during the daytime none 

 are visible, but in the evening they commence to crawl about 

 quite actively. 



Again, a large number of conspicuously-coloured larva? are 

 also hairy ; with the exception of the cuckoo, birds dislike 

 hairy larviB ; it may be also difficult to pick them up, or they 

 may escape with the trifling loss of a few bunches of hairs. 



Among the " Tussock " moths, the localisation of the hairs 

 into tussocks (see figure of Vapourer Moth caterpillar on 

 p. 160), and the attitude assumed by the caterpillar, almost 

 compels the bird to peck at these thick bunches; other larvae 

 produce odoriferous secretions, which are, probably, at least 

 as effective as their appearance in keeping off enemies. Still 

 there is no reason why a caterpillar should not have more 

 than one means of defence at its command ; there are some 

 species, indeed, which undoubtedly have. For example, the 

 larva of the " Puss " moth : its general green coloration may 

 be fairly considered protective ; if discovered it can adopt a 

 terrifying attitude and eject a quantity of formic acid ; the 

 flagella may perhaps be considered rather as a weapon for 

 warding off the attacks of ichneumons than for repelling- 

 vertebrate foes. 



Warning Colours can only be safely adopted by a comparatively 

 Small Number of Animals. 



It has been pointed out by Mr. Poulton that warning colours 

 can only be safely adopted by a small proportion of the insects- 

 in any country. The means of defence is so simple that it is 

 remarkable not to find more examples of it ; but this result, 

 is prevented by reason of the fact that a too complete success 

 would frustrate its objects : if all insects became distasteful 



