THE COLOURS OP DESERT ANIMALS 149 



at night, and spend most of the daylight hours 

 visiting flowers or sucking the blood of the larger 

 animals. Certain flies of the famiHes BombyUidae 

 and Nemestrinidae exhibit the same type of colora- 

 tion, though they spend their time at flowers or 

 hovering in the air : they do not rest on the soil 

 which they so closely resemble in colour. 



We find, then, that most of the animals which live 

 in deserts are coloured buff or sandy or pale grey ; 

 bold pattern is rare ; this type of colour is exhibited 

 by animals of nearly every group, and is prevalent 

 in the deserts of every continent. It is even char- 

 acteristic of some insects, not closely related to one 

 another, which spend the hours of daylight in the 

 air or on flowers and not on the surface of the 

 desert. As to the effect of these colours upon the 

 human eye it must be acknowledged that the 

 prevalent buff and sandy colours of desert animals 

 do render them extremely difficult to detect, unless 

 they move. This is probably as much due to their 

 immobility as to their colour. Every naturahst 

 who has ever visited the desert has noticed this, 

 and it is true of all the manifold forms of life which 

 exhibit these colours. The most remarkable exam- 

 ple that ever came to my notice was in Baghdad, 

 Mesopotamia, in September. There was a small 

 patch of ground of perhaps an acre, walled off but 

 not at that season cultivated. In it one could always 

 be certain of flnding at least a score of Egyptian 

 Nightjars {Caprimulgus cegyptius), but though the 

 ground was absolutely bare, and though I visited 

 the place repeatedly, I never succeeded in detecting 



