V 



1.^ 



RELATIONS OP ANIMALS AND PLANTS 123 



by the plant kingdom to the animals. It must be 

 remembered that in the desert this source of water 

 is of much greater importance than it is imder 

 other conditions. In most environments the water 

 which is part of the food material is incidental : 

 in the desert it is essential, and commonly the only 

 available supply. 



We have already (Chapter III) divided the 

 desert flora into three biological groups — the annuals, 

 the perennials which he buried during the un- 

 favourable season, and the perennials which exist 

 above the surface of the ground at all seasons. 

 Let us see how each of these groups is used by the 

 animals as a source of food and water. 



The conditions which are best for the annuals, 

 and which lead to the production of abundant annual 

 vegetation after rain has fallen, are favourable also 

 to many animals. No sooner have the young annual 

 lants appeared above the earth than they are 

 attacked by numbers of caterpillars, bugs, leaf -eating 

 beetles, wood-Hce, and other plant-eaters : as soon as 

 the blossoms open they are visited by bees, butterflies, 

 moths, thrips, flower-eating beetles, and many other 

 small creatures in search of nectar or pollen or 

 petals. For a very short time the cUmate and the 

 floral environment is favourable to insects in 

 general. Then the soil dries, the air becomes hot, 

 and most of the flowers and insects disappear. 



The majority of insects which are dependent on 

 the annual vegetation in the Great Palaearctic 

 Desert are active for a very short period and exist 

 through the dry nine months of the year in a state 



