WARNING COLOUES 181 



Natural selection has enabled certain animals to eat 

 unpalatable Insects with apparent relish 



Naturalists have always recognised that an insect 

 may be distasteful to one animal, but palatable to 

 another. It is, however, very probable that these 

 differences have been acquired comparatively recently, 

 and have arisen out of the competition for food. In 

 most cases the change of habit has not become so far 

 confirmed that the previously distasteful food is eaten 

 with avidity and pleasure. Again, when we find that 

 the taste of an insect is recognised as nauseous by a 

 standard w-ide enough to include mites and spiders as 

 well as birds, lizards, and frogs, it appears probable 

 that any difference of opinion is due to an altogether 

 exceptional immunity conferred upon certain species 

 by natural selection. 



Nauseous qualities probably do not affect Insect 

 parasites 



It is probable, however, that this argument does 

 not apply to insect parasites, which are not in the 

 position to gratify their tastes, but must make the 

 best of the larva in which the parent has deposited 

 her eggs. It is clear that even the most nauseous 

 forms must suffer greatly from the attacks of enemies, 

 for the average number of individuals in each species 

 appears to remain constant. It is likely that the 



