312 THE COLOURS OF ANIMALS 



he believes that scope has thus been given to the causes 

 which have produced the sexual adornment. This 

 argument of course holds good, even if we are com- 

 pelled to reject the causes suggested by him. A still 

 better example is afforded by the Australian pigeons, 

 which ' are sometimes adorned with colours vying 

 with those of the gayest parrots and chatterers.* Mr. 

 Wallace explains this fact as due to ' the entire absence 

 of monkeys, cats, lemurs, weasels, civets, and other 

 arboreal mammals ' ; while the green colour of the 

 upper part may be due to the need of concealment 

 from birds of prey. In some small islands of the 

 Pacific, where such foes are very scarce, the pigeons 

 may assume a rich yellow colour.^ We see the same 

 tendency in those predaceous insects which have little 

 to fear, and which are swift enough to catch their 

 prey without attempt at concealment. 



The dangers of bright sexual colouring may be averted 

 by extreme wariness 



In many cases the danger incurred by the attain- 

 ment of sexual colours may be balanced by the special 

 development of some quality such as extreme wariness. 

 I was very much struck by the opposite kinds of 

 colouring exhibited by the fish which were extremely 

 abundant at low water in the rock pools at Orotava, 

 Teneriffe. The colours of some were extremely beauti- 



* Wallace, Distribution of Animals, vol. i. p. 395. 



