ANIMALS— PHYSICAL ENVIRONMENT 69 



is bare of leaves till the warm weather is well 

 advanced, and it is possible that the species Hes 

 dormant through the spring as egg, or resting larva, 

 or pupa, until the Caper bush is in fuU leaf. On 

 the other hand, it is possible that even the mild 

 winter of Mesopotamia is fatal to T. fausta in all 

 stages, and that it recolonizes this country every 

 spring by immigration from lands with warmer 

 winters ; in Palestine it seems extremely probable 

 that this species dies out every winter, and recolonizes 

 the land every spring. 



It is convenient to mention here another Pierine 

 butterfly which eats Caper, the species known as 

 Belenois mesentina, although it was apparently 

 absent from Amara. It is a species which often 

 occurs in great numbers in very hot places, even in 

 the hottest weather : for instance, along the North- 

 West Frontier of India it is common from May to 

 October, a season during which the other butterflies 

 are scarce or not on the wing at all. It has an 

 extremely wide distribution, from tropical Africa to 

 India, and is by no means confined to deserts. This 

 wide distribution is possibly due to its ability to 

 continue active life at a time of year when heat 

 and dryness have caused most butterflies to cease 

 from flying, and this activity in the height of summer 

 may in turn be due to the fact that the Caper is 

 one of the not very numerous plants in full leaf at 

 that season. 



It must be admitted that this study of the number 

 of species of insects on the wing in various months 

 is liable to one very grave criticism. Each group 



