THE VARIATION OF THE IMAGINES OF THE LEPIDOPTERA. 67 



yellow, the further coloration of the pigment giving rise to the special 

 coloration of the scales. Xanthic patches, sometimes extending to a 

 whole wing, at others to the whole insect, are exceedingly common in 

 Satyrid and Argynnid butterflies, and appear to be due to an arrest of 

 the development of the pigment in the whitish or ochreous stage. 



The instances of protective resemblance already referred to, remind 

 us at once of the particular case which has been brought under our notice 

 by Wallace, Weismann, Niceville, and others, w^., that affecting the "leaf 

 butterflies " of the tropics. In the instances we have hitherto con- 

 sidered, the resemblance of the insect has been to the surface upon 

 which it rested, gaining its protection by its resemblance to that sur- 

 face as a whole. In the case of the " leaf butterflies," the resemblance 

 is to a special definite object, viz., the leaf of the particular tree on 

 which the insect rests. These butterflies are Nymphalids, and belong 

 to the oriental genus Kallima, the Indian species paralekta, inachis, 

 and philarcJnts being nearly four inches in expanse, while the African 

 species, K. rumia, is smaller. These butterflies are conspicuous objects 

 when flying, but when they alight upon a twig, the wings raised over 

 the back, and the fore-wings thrown well forward, the pattern and 

 colour of the undersurface are such that they make a perfect resem- 

 blance to a leaf. The mid-rib consists of a coloured stripe crossing 

 both wings, which, taking its rise at the apex of the fore-wing, is con- 

 tinued over the hind-wing, and terminates in a tail-like extension of 

 the latter, the extension just reaching the twig, and thus resembling 

 the petiole of a leaf. 



But the similarity of colouring between some of the unprotected 

 Pierids and the nauseous Nymphalids, is, perhaps, more remarkable. It 

 is well known among entomologists that many of the latter are specially 

 protected from the attacks of birds, and other insect-eating animals, 

 by the production of various scents, which make them distasteful and 

 objectionable as articles of food. On the other hand, the Pierids of 

 which our common white and yellow butterflies are good examples 

 appear to be particularly subject to the attacks of numerous enemies. 

 Bates, Trimen, and other observers have noticed that in the tropics, 

 the Pierids, flying with the Nymphalids, frequently lose the ordinary 

 Pierid coloration and type of markings, and become orange-coloured, 

 and marked on the same general lines as the common Nymphalids. 

 So similar are the colour and markings in some instances, that even 

 specialists have been, for a time, deceived, and have failed at first to 

 recognise them, not only as belonging to different families, but even 

 as distinct species. That this similarity served the purpose of protec- 

 tion to the Pierid was first propounded by Bates, and it soon became 

 generally accepted as an explanation of the facts, that the Pierids, 

 owing to their similarity to the nauseous Nymphalids, were less likely 

 to be attacked by birds and other insectivorous animals, which had 

 learned by experience that insects of a certain colour were objectionable 

 as articles of diet. 



We frequently find that when the sexes of a given species vary 

 much in Habit, there is considerable difference in the colour, and less 

 often in the markings, of the sexes. Sometimes, too, there is con- 

 siderable sexual diversity when the habits are very similar. Many 

 species have the males brilliantly coloured in comparison with the 

 females ; frequently the sexes are almost identical in tint, but the 



