WARNING COLORATION. 173 



Lave been largely neglected by those who have thought and 

 written upon the subject ; but it may be reasonably urged that 

 one would not expect to meet with valuable physiological 

 observations in a work devoted to a small group of Annelids. 



Dr. Eisig points out, as has been already mentioned in this 

 book (p. 127), that pigment in the skin has been actually 

 proved in some cases to be excreted matter ; and it may be so 

 in other cases where no direct evidence is forthcoming'. 



In earlier times, when there were no birds and after all, 

 the chief enemies of caterpillars are birds brilliant colora- 

 tion, due to abundant and varied pigment, would be the rule. 

 Dr. Eisig is of opinion that this pigment is itself largely the 

 cause of the distastefuluess.* If so, we arrive at an interesting- 

 conclusion that the. brilliant colours (i.e. the abundant secretion 

 of pigment) ham caused the inedibility of the species, rather 

 than that the inedibility has necessitated the production of bright 

 colour as an advertisement. 



This is an important alteration in the usual view of warning 

 colours ; but it is obviously not entirely antithetical to the 

 views of Wallace, Poulton, and others ; for we may still sup- 

 pose that the bright colours are actually "warning" colours, 

 although they have not been evolved for this express purpose. 



On the view advocated here brilliant coloration is the 

 normal condition of caterpillars ; the advent of bird-life 

 proved a disastrous event for these animals, and compelled 

 them to undergo various modifications, except in the case of 

 those forms which combine brilliant coloration with uneatable- 

 oess. 

 Dr. Eisig's ingenious suggestion may possibly apply to 



I may remark that a Cebus monkey sucked a Magpie caterpillar, and 

 threw away the skin, as a boy sucks an orange and disposes of the peel. 

 This is so far evidence that the pigmented skin is the distasteful part. 



