THE COLOURS OF DESERT ANIMALS 153 



byliinse, and (b) the Anthracinse, a sub-family in 

 which this phenomenon is quite common. 



In the Algerian Sahara among the numbers of 

 active black Adesmia one may frequently capture 

 a large Long-horned Grasshopper, black and shiny, 

 with red processes on the thorax. This insect is 

 Eugaster guyoni. In contrast to the active Adesmias, 

 it is a very sluggish insect and its hindlegs are not 

 specially lengthened and strengthened for jumping 

 as they are in nearly all its relatives. Further, we 

 may suppose that Adesmia and the other diurnal 

 Tenebrionidse are black by inheritance, and that 

 they have retained the family's colours not because 

 it was directly advantageous, but because it was not 

 disadvantageous. No such reasoning can be appUed 

 to Eugaster, which belongs to a family in which 

 shiny blackness is extremely rare : we are therefore 

 left to wonder at its assumption of this colour and 

 at its abrogation of the power to jump. Eugaster 

 is extremely conspicuous and deliberate in its 

 motions ; when it is handled it pours forth a copious 

 brown oily secretion, and it is tempting to suppose 

 that this protects it from insect-eaters ; we have 

 absolutely no evidence that this is the case. 



Among the Short-horned Grasshoppers (Locus- 

 tidse or Acridiidae) there is an interesting species, 

 CalUptamus coelesyriensis, which ranges from Pales- 

 tine to Turkestan. In Palestine it occurs in semi- 

 desert country among withered annual vegetation in 

 the months of May and June. One common form 

 is very dark chocolate brown all over, except that 

 the ventral surface is slightly paler. I have nearly 



