114 ANIMAL LIFE IN DESERTS 



fications either of structure or of habit. This is seen 

 in the case of caterpillars of the famiUes Arctiidae, 

 Lymantriidae (Liparidae), and Lasiocampidae. These 

 hairy caterpillars are abundant in the semi-deserts 

 of Algeria, Southern Palestine, and other countries 

 in the spring-time. In places where the annual 

 vegetation is not too dense one may see them roUed 

 up and blown along the ground for many yards by 

 a gust of wind. They are not more hairy than their 

 congeners in Europe, so that in this case we have a 

 number of insects which are able to benefit by the 

 desert winds without modifying either their habits 

 or their structure. 



Of the destructive effect of desert wind upon small 

 creatures, especially small winged creatures, very 

 little is known. It is on record that small birds 

 have been dashed against a waU and killed in the 

 Hebrides, and there is every reason to suppose 

 that the violent winds which occasionally visit some 

 deserts are equally destructive. The destruction of 

 swarms of locusts by wind which blows them into 

 the sea has been famihar since the dawn of history. 



V. Relationships with Soil 



There is no doubt that each type of desert soil 

 presents its special problems to the fauna and flora 

 and is inhabited partly by generaHzed forms which 

 are able to exist in many types of desert or even 

 outside the desert, and partly by specialists which 

 are limited to clay or rock or sand, or other special 

 soil. Information on these points is at present very 

 meagre and fragmentary, except with regard to the 



