CONTENTS xv 



among mating animals Battles to ensure the healthiest 

 mating among spiders, fish, birds, and mammals Testing 

 oi the powers in drones of the bee and males of other 

 insects Unequal severity of the test for survival among 

 young males in contrast to the young females of many 



animals 190 



Eggs and young Migration The sea as a nursery The 

 advantages of pelagic larval life Modes of defending the 

 eggs and young of aquatic animals by fixing them to some 

 holdfast and by the guardianship of the parents The nests 

 and nurses of fish The protection of the eggs by frogs and 

 reptiles The secretiveness of birds and insects in their 

 choice of nesting sites Brief review of the nests of birds 

 Small birds construct the most carefully woven nests The 

 significance of the relation between size and incubating 

 heat The varied methods employed by insects The 

 elaboration of nurseries by social insects .... 201 



CHAPTER X 



THE LIFE-HISTORIES OF INSECTS 



The influence of climate in stimulating the development of 

 insect life The cyclic changes of its abundance The 

 insects of early spring Selection of nesting sites Differ- 

 ences between families of great and of lesser antiquity in the 

 food of the young 217 



The life-histories of primitive insects The spring-tails and their 

 allies The straight-winged insects Grasshoppers, locusts 

 The difficulty of shedding the old skin The development 

 a gradual one The life-history of the dragon-fly May-flies 

 and their larvae 222 



More complex life-histories Metamorphosis The introduc- 

 tion of the pupal stage Caddis-flies and caddis-larvae 

 The development of the pupal stage and the emergence of 

 the fly Beetles The life-history of the oil-beetle . .234 



The life-histories of more modern insects Butterflies and 

 their adaptations to aerial life The development of the 

 cabbage-white butterfly Complex structural changes 

 during the pupal stage The Diptera or two-winged flies 

 Their economic importance The mosquito and midge 



