V] SOME CRITICISMS 55 



though this is by no means always so. Many Eu^oloeas 

 are sombre inconspicuous forms, and it is only some 

 of the Ithomiines that sport the gay colours with which 

 that group is generally associated. The members of 

 the distasteful groups usually present certain other 

 pecuHarities. Their flight is slower, they are less 

 wary, their bodies are far tougher, and they are more 

 tenacious of life. The slow flight is regarded as an 

 adaptation for exhibiting the warning coloration to 

 the best advantage, but from the point of view of 

 utihty it is plausible to suggest that the insect would 

 be better off if in addition to its warning coloration 

 it possessed also the power of swift flight i. It is 

 possible that the peculiar slowness of flight of these 

 unpalatable groups is necessitated by the peculiar 

 tough but elastic integument which may present an 

 insufficiently firm and resistant skeletal basis for 

 sharp powerful muscular contraction, and so render 

 swift flight impossible. It is stated that the flight 

 of the mimics is like that of the model, and in 

 some cases this is undoubtedly true. But in a great 

 many cases it certainly does not hold good. Papilio 

 clytia (PI. I, figs. 7 and 8) is a strong s\vift flyer 

 very unlike the Danaine and Euploeine which it is 

 supposed to mimic. The flight of the female of 

 Hypolimnas misippus (PI. IV, fig. 7) is quite distinct 

 from that of Danais chrysippus, whfle the mimetic 



^ These "unpalatable" butterflies are sometimes extensively 

 preyed upon by insectivorous birds, when they fall an easier prey owing 

 to their slowness (cf. p. 112). 



