442 NATURAL HISTORY [chai\ xviii. 



zarinda, a native of Celebes, compared with the much 

 shorter wing of Tachyris nero, a very closely allied species 

 found in all the western islands. The difference of form 

 is in each case sufficiently obvious, but when the insects 

 themselves are compared it is much more striking than 

 in these partial outlines. 



From the analogy of birds, we should suppose that the 

 pointed wing gave increased rapidity of flight, since it is a 

 character of terns, swallows, falcons, and of the swift- 

 flying pigeons. A short and rounded wing, on the Other 

 hand, always accompanies a more feeble or more laborious 

 flight, and one much less under command. We might 

 suppose, therefore, that the butterflies which possess this 

 peculiar form were better able to escape pursuit. But 

 there seems no unusual abundance of insectivorous birds to 

 render this necessary ; and as we cannot believe that such 

 a curious peculiarity is without meaning, it seems probable 

 that it is the result of a former condition of things, when 

 the island possessed a much richer fauna, the relics of 

 which we see in the isolated birds and Mammalia now 

 inhabiting it; and when the abundance of insectivorous 

 creatures, rendered some unusual means of escape a 

 necessity for the large-winged and showy butterflies. It 

 is some confirmation of this view, that neither the very 

 small nor the very obscurely coloured groups of butterflies 

 have elongated wings, nor is any modification perceptible 



