EECOGNITIOX-MAEKS 185 



possible for the colour-development to attain a degree of 

 variety and beauty beyond that of all other living things. 

 The larvae of Lepidoptera in their countless myriads un- 

 doubtedly constitute an important factor in supporting the 

 gloriously varied bird-life of the tropics, as we have seen 

 that they so largely support that of our temperate ^nes. 

 It is the comparatively small surplus that escapes which is 

 yet ample for the development of the perfect insects in such 

 abundance as to keep up an approximately equal supply of 

 larva? for the next generation of birds. When this is done they 

 themselves become the prey of birds, lizards, and other insect- 

 eating animals. 



Some General Conclusions from Recognition-Marks 



We have thus been led by the study of colour as a means 

 of recognition by birds and mammals to some very important 

 general conclusions. The first is, that in both these groups, 

 it has primarili/ a still more important function, that of facili- 

 tating the formation of new species during the early stages 

 of adaptation to changed conditions of life. Its secondary, 

 but still very important use in many groups, is for easy identi- 

 fication as alreadv described. That this is the true state of 

 the case is rendered almost certain by the occurrence of a 

 large number of species in which the markings for recognition 

 are noiv unnecessary though they were of the highest impor- 

 tance during the initial stages of evolution. 



Another and still more curious result of the study of this 

 subject is the evidence it affords that the most varied in colour 

 and markings ' of all insects — the butterflies — do not, pri- 

 marily, recognise each other by sight, but by some sense 

 analogous to that of smell. This seems now to be almost cer- 

 tain, and it affords the explanation of what would otherwise 

 be a great difficulty, how the males of polymorphic females, as 

 in Papilio pammon in the East and Papilio apneas in the West, 

 numerous American Pieridir and many other groups, in which 

 the females are coloured as if with the purpose of being as un- 



