FEEDING-HABITS OF FISH AND BIEDS. 55 



It has therefore been concluded that on broad lines butterflies are less 

 palatable than many other insects, and that their diurnal habits, relatively 

 slow flight, and conspicuousness may be looked upon as warning characters. 



The wings of butterflies, apart from pattern and coloration, are conspicuous 

 on account of their large size (size is a very powerful factor as regards 

 visibility), and also on account of their opacity [transparent wings are a 

 great aid to concealment). Although butterflies as a whole may be less 

 palatable than many other insects, it does not follow that among them there 

 may not be difference in palatability, just as there is in the Ephemeroptera 

 towards fish and birds ; and just as butterflies may as a whole exhibit con- 

 spicuous (warning) characters so, among them, according to their palatability, 

 some may exhibit more conspicuous characters than others. If animals can 

 be arrranged in an order of palatability, and if warning coloration and 

 protective resemblance are the result of selection by enemie?, then animals 

 liable to attack should also form a series presenting all grades, from a most 

 pronounced conspicuous coloration to a great protective resemblance, the 

 intermediate forms showing something of both. Some evidence h;is been 

 brought forward that this occurs in the Ephemeridse. In a previous 

 paper (5), the factors for conspicuous pattern were ascertained by experiment 

 ■with artificial pattern, and it was shown that among Indian Lepidoptera 

 some of the insects present all the factors for conspicuousness ; others, some 

 only; whilst others, only a few. Swynnerton (2) has shown that animals, 

 which form the food-supply of any species, can be arranged in order from 

 the most palatable to the least palatable ; and opinion is expressed that 

 animals bear some distinctive mark whereby a preyer can recognise and 

 distinguish the relatively unpalatable from the relatively palatable. The 

 "distinctive'" coloration need not necessarily be very conspicuous. Unpalat- 

 able animals can afford to cany a conspicuous mark, but the relatively 

 palatable can only carry one, which is to a small extent conspicuous, or one 

 which is only displayed when concealment has failed. 



This conception is similar to the author's, but is better in that, by 

 replacing the term " warning coloration," it brings into line those slightly 

 conspicuous characters which cnnnot be called " warning " characters. The 

 conception presumes that preying animals have a memorising power of con- 

 siderable magnitude, but this presumption does not appear to be always 

 necessary : for instance, a very strong family likeness runs through lono- 

 series of protected species of butterflies. Swynnerton says of this, " This can 

 be accounted for by the advantage of maintained notoriety." If, however, 

 a number of different butterflies present very conspicuous characters, they 

 must be very similar in appearance, because the majority of the factors for 

 conspicuousness must be present in each, l'oulton (3), so long ago as 1887, 

 observed that certain colours and patterns associated with unpalatabilitv, 



