118 MIMICRY, AND OTHER PROTECTIVE 



ings as to make them specially visible. Mr. Darwin 

 had put the case to me as a difficulty from another 

 point of view, for he had arrived at the conclusion that 

 brilliant colouration in the animal kingdom is mainly 

 clue to sexual selection, and this could not have acted 

 in the case of sexless larvse. Applying here the analogy 

 of other insects, I reasoned, that since some caterpillars 

 were evidently protected by their imitative colouring, 

 and others by their spiny or hairy bodies, the bright 

 colours of the rest must also be in some way useful to 

 them. I further thought that as some butterflies and 

 moths were greedily eaten by birds while others were 

 distasteful to them, and these latter were mostly of con- 

 spicuous colours, so probably these brilliantly coloured 

 caterpillars were distasteful, and therefore never eaten 

 by birds. Distastefulness alone would however be of 

 little service to caterpillars, because their soft and juicy 

 bodies are so delicate, that if seized and afterwards re- 

 jected by a bird they would almost certainly be killed. 

 Some constant and easily perceived signal was therefore 

 necessary to serve as a warning to birds never to touch 

 these uneatable kinds, and a very gaudy and conspi- 

 cuous colouring with the habit of fully exposing them- 

 selves to view becomes such a signal, being in strong 

 contrast with the green or brown tints and retiring 

 habits of the eatable kinds. The subject was brought 

 by me before the Entomological Society (see Proceed- 

 ings, March 4th, 1867), in order that those members 

 having opportunities for making observations might do 

 so in the following summer ; and I also wrote a letter to 



