178 THE COLOURS OF ANIMALS 



shown to be extremely nauseous, and the two latter 

 emit a very unpleasant smell. 



The sting possessed by the females of so many 

 Hymenoptcra is obviously an unpleasant attribute, . 

 rendering the insect disagreeable or even dangerous to 

 eat. We find accordingly that stinging insects are 

 often rendered conspicuous by warning colours, of 

 which the contrasted dark and yellow bands of the 

 Common Wasp, the Hornet, and of many Humble 

 Bees, furnish examples. 



Warning Colours are also to be found in other 

 orders, but it is unnecessary to give further examples. 

 They will be recognised in numbers in any country 

 walk during the summer, although the experimental 

 proof of the co-existence of some unpleasant attribute 

 is still wanting in a large proportion of the cases. 



Warning Colours can only be safely adopted by a small 

 proportion of the Insects in any country 



The acquisition of an unpleasant taste or smell, 

 together with a conspicuous appearance, is so simple 

 a mode of protection, and yet apparently so absolutely 

 complete, that it seems remarkable that more species 

 have not availed themselves of it. What can be the 

 principle which works in antagonism to such a mode 

 of protection? Thinking over this subject, as the 

 result of a lecture upon the facts and conclusions 

 already described, 1 it appeared probable that such an 



1 Delivered at the Royal Institution in the spring of 1886. 



