ANIMALS— PHYSICAL ENVIRONMENT 65 



or other conditions, upon particular species, our 

 knowledge will become more accurate. We shall 

 perhaps find that in the case of one creature the 

 cessation of activity during summer is induced by a 

 mean temperature above a certain degree, or in 

 another by a minimum daily humidity below a 

 certain percentage. Until the particular effect of 

 altered cUmatic conditions upon selected species of 

 animals has been studied we cannot do more than 

 record the facts, which are that the great majority 

 of the invertebrata in deserts undergo periods of 

 dormancy either in winter or in summer, or both. 



In Mesopotamia it is easy to notice that insects 

 are commonest after the winter rains, during the 

 temperate spring and early summer. From April 

 to June nearly aU insect life is fully active, and its 

 activity coincides with and follows the rapid growth 

 and blossoming of the spring vegetation. During 

 the hot dry months of summer the insects are not 

 in evidence ; as the weather becomes cooler there 

 is a distinct, though less evident, increase in the 

 number of insects on the wing. Figs. 28 to 30 are 

 compiled from collections made at Amara, R. Tigris, 

 by Capt. W. E. Evans, R.A.M.C., and myseK. 

 , It would scarcely be extravagant to claim that our 

 collections are a fair random sample of the fauna 

 of Amara at all seasons. We had few distractions 

 and were deeply interested in entomology ; we each 

 resided in Amara for almost exactly one year ; we 

 felt that we were in an imknown land and there- 

 fore collected everything, even species which were 

 common, in long series when we could; we could 



