298 THE BIOLOGY OF INSECTS 



haunches of the hind-legs are behind the tail segment. 

 These little bugs crawl on coral reefs, shelter beneath large 

 dead bivalves ten feet below high-water mark, or skim over 

 the surface of the sea in the channels north of Australia 

 and on the coast of East Africa. Their adaptations for 

 marine life are somewhat similar to those of Halobates, 

 but they do not appear to venture far out on the waters of 

 the ocean. The modification of these members of the 

 typically aerial class of insects for life in or on the salt water 

 makes them of great interest among the assemblage of 

 ** small and great beasts " that dwell in the shallows, the 

 depths and the expanses of the wide sea. 



In this survey of the adaptation of insects to the various 

 haunts in which they live some reference has been made 

 to the correspondence of their life-cycle to the changes of 

 the seasons. Some examples that illustrate especially this 

 correspondence may now be given. In tropical regions 

 where insect life is most abundant there may be com- 

 paratively slight seasonal change during the course of the 

 year, and generations of a species of insect follow each other 

 without any special need of adaptation to meet marked 

 variations in temperature or humidity. It is rather in the 

 temperate regions of the globe, and in the far north and 

 south, where a proportion of all resident living creatures 

 have to survive a winter of more or less severity, that seasonal 

 adaptations can be most readily and conveniently studied. 



Examples taken from among the insects of our own 

 country serve well, therefore, for a discussion of this aspect 

 of insect life. A general survey of the relation between 

 insect life-histories and the course of the seasons demon- 

 strates that the creatures' life- cycles are definitely adapted 

 to the changes of temperature through the year and the 

 resulting changes of conditions of the surroundings, especially 

 with regard to the rise and fall in the abundance of vegetation 

 that aflFect the food supply. It is evident that insects 

 resident in our northern regions must be able to survive the 

 winter in some stage of their life-history, and among a 

 variety of insects of diflFerent groups we find all stages— 



