2 PREFACE. 



difficulty in discriminating and identifying insects, though, at the same time, the scientific vahie 

 of the study would be largely reduced ; but it is not so. First we find that in some species the 

 sexes are differentiated — the females differing from the males either in colour or style of markings, 

 and even in form and outline of the wings, these differences being constant in each sex. Again, 

 we find that in different climates Butterflies, apparently the same in general character, present 

 constant differences in colour or style of marking of more or less importance, but frequently 

 sufficient to justify the description of each form under a separate name. Again, in different 

 localities, even where the differences of climate are inappreciable, such as notably the various 

 islands of an archipelago, and in a lesser degree disconnected valleys of a mountain range, the 

 Butterflies of each locality often present constant and well marked differences, particularly in 

 the size and extent of markings, thus forming what have been termed "geographical" varieties 

 in contradistinction to " climatic " varieties ; and yet, again, we have the most interesting and 

 important variation of all occurring among Butterflies which have two or more broods in the 

 year ; and in which the summer and autumn broods differ from the spring brood more or 

 less, sometimes so widely in colour and markings that, until the question was conclusively set 

 at rest by breeding Butterflies of the one type from the eggs of Butterflies of the other, the 

 two forms were described and universally accepted as representing two distinct species. 



Thus we have '"sexual," "climatic," "geographic," and "seasonal" variations, each of 

 which can be referred more or less confidently to known external causes ; but, in addition to 

 these, the study of the subject is complicated by individual variations, which appear to be 

 ouite irrespective of external conditions ; such variations are exhibited in different species in 

 different degrees, or possibly the tendency to vary may pass through more or less active or 

 dormant stages at different epochs of the history of each group. At the present time some 

 species, notably among the yiinonias, are wonderfully constant to the type ; others, again, 

 differ so universally among themselves that scarcely any two specimens, even from the same loca- 

 lity, are alike. Of such variations the under-surfaces of the wings in Melanitis leda and M. ismene, 

 and in the great " oak-leaf " Butterflies of the genus A'(7///wa, are noteworthy instances; also 

 the numbers and size of the ocelli in many genera of i\\Q Satyri7icz : and, again, instead of a 

 single typical form, with minor differences in each individual, we sometimes find, as in the case 

 of Papilio polytts or P. iiiemnon, that there are several distinct types, described by the earlier 

 authors as distinct species, t)ut which in reality spring promiscuously from the same stock — 

 a single batch of the eggs laid by a single female having been found to produce two or more 

 of the different forms. And, lastly, we find that specimens aberrant from the type occur singly 

 and casually here and there from time to time, and coexisting in the same localities with speci- 

 mens of the normal form. It may easily be conceived that among insects with ssuch manifold 

 tendencies to variation and such brief periods of existence, the clue to the laws which govern 

 such developments may most readily be found. 



The phenomenon of "mimicry," too, is deserving of the closest scientific obsei"vation. 

 One of the earliest puzzles met with by the observer of Butterflies lies in finding males and 

 females in company, apparently belonging not only to different species, but different genera, 

 and even families ; but closer examination reveals that the female in reality belongs to the 

 same species as the male, although its coloration and markings are excellent imitations of a 

 totally different Butterfly, generally of a much commoner Butterfly, and almost always of a 

 Butterfly less subject than its own species to destruction by birds and reptiles. The subject is 

 too extensive to enter on here, but it is one that should never be lost sight of in investigating 

 the life-history of insects. 



The field for observation offered by the British Indian Empire is as varied as it is vast. 

 We have every climate, from the eternal snows to the tropics— and all the most interesting 



