250 INSECT TRANSFORMATION 



the creature's special mode of life. The peculiar characters 

 of any insect larva are adaptive characters fitting it for its 

 surroundings and its mode of feeding, enabling it to meet the 

 drawbacks and changes of its special life-conditions, which 

 differ in almost all cases from those of the perfect insect. 

 Where as in the case of the cockroach or grasshopper the 

 young lives under the same conditions as the adult, it resembles 

 the adult, not only in the great main features of its body-form, 

 but in most points of detail as well. The problem of insect 

 transformation is thus seen to be a problem of the explanation 

 of the origin of many adaptive features in the early life-stages 

 of highly-specialized animals. 



This view of the transformation of insects helps us to meet 

 the difficulty mentioned above that the most highly-organized 

 members of the class undergo the most striking changes. In 

 the more primitive orders the newly-hatched insect resembles 

 its parent and throughout the stages of its life-history it lives 

 and feeds in much the same way as its parent does. Such, 

 for example, is the case with a spring-tail or a cockroach. In 

 the more highly-specialized orders the student is struck by 

 marked contrasts, like that between the house-fly and its 

 maggot or between the hive-bee and its grub. All the evidence 

 points to the working out of a process of divergent evolution 

 between the preparatory and the perfect stages ; in these 

 most advanced insects the adult has become more and more 

 elaborated, and the larva more and more degraded as compared 

 with the adult. This general conclusion as to the history of 

 insect metamorphosis is now upheld by most students of the 

 subject. We have seen how among the beetles (Coleoptera) 

 a series of larval forms can be traced showing increasing 

 divergence from the adult. Where within this order there 

 are different larval forms in the life-history of the same species 

 (as in the hypermetamorphosis of the oil-beetles), the active 

 armoured larva with relatively long legs precedes the soft, 

 short-legged grub, and where the larval jaws differ least from 

 those of the adult (as in the case of Dascillus and Helodes, 

 p. 104) the presence of distinct maxillulae emphasizes the 

 primitive standing of the type. It thus becomes clear that 

 the maggot represents the greatest departure from the primitive 

 condition among insects, and we understand how with 



