INFANCY OF CRABS AND CATERPILLARS 257 



be, with resplendent wings, but a horde of murderous 

 ichneumons which speedily enter upon their hideous 

 work. 



In order that an idea may be gained of the part these 

 ichneumons play in preventing the undue increase of 

 caterpillars, the reader should collect, say, fifty cater- 

 pillars of the common cabbage-white butterfly ; and he 

 will find that of these only a small fraction will ever 

 become butterflies. The majority of these butterfly 

 children are destined to nourish the offspring of their 

 relentless enemy ! 



It will be clear that we cannot enlarge upon the life- 

 history of these remarkable insects when we mention 

 that over 1,200 species of ichneumon flies are to be met 

 with in Great Britain alone ! 



17 



