THE COLOURS OF ANIMALS AND PLANTS 141 



signal of danger to the other rabbits ; and when 

 feeding together, in accordance with their social 

 habits, soon after sunset or on moonlight nights, the 

 upturned tails of those in front serve as guides to 

 those behind to run home on the appearance of an 

 enemy. Many birds, antelopes, and other animals, 

 have markings believed to serve a similar purpose, 

 and probably the principle of distinctive colouring 

 for recognition has something to do with the great 

 diversity of colour met with in butterflies. 



Epigamic Coloration. 



This is seen in mature animals, especially in 

 butterflies and birds, where the two sexes differ 

 markedly as regards colour. As a general rule, the 

 male is of the same hue as the female, but of a 

 deeper and more intensified colour : for instance, in 

 thrushes, hawks, and in the Emperor moth. 

 Sometimes patches of colour found in the males 

 are absent in the females, as in the Orange-tip 

 butterfly. In some cases there are more extreme 

 differences, as in the drake, peacock, cocks and 

 hens, pheasants and Bird of Paradise ; gay colours 

 being the special privilege of the male. (Fig. 26.) 



It is curious to note how with man the conditions 

 are reversed, for the female butterfly or bird is as a 

 rule larger and plainer than her mate. So it is 

 with the organs of voice ; the male cricket or grass- 

 hopper can alone produce sound, and many female 

 birds have no song. The power of talking was 

 originally the exclusive possession of the males — a 



