INTRODUCTION. 13 



, without much difficulty, be discriminated. Throughout the families in Tfhich the forelegs 



are more or less imperfectly developed, including the Danaimr, Satyrina, Elymniina, Morphine, 

 AcraiiKV, Nymphalimt, LibytJucina, NemcobUmr ^ and Lycitnidit, the structure of the tarsus of 

 the imperfect foreleg differs in the male and female. These differences vary in the different 

 genera, (see Pi. I, dissections oijumntia asteric, Elymnuis umiularis and Melanitis Iciin, figs. 

 e. and/) and are detailed in the generic descriptions. In addition to the " foreleg" test the 

 sexes of many species belonging to the above families may be recognised by marks on the 

 virings, which occur in the male sex only. Such are the pouches on the hind wing of many species 

 of Danais, the patches of silky appressed scales on the forewing of many species of Euplcea, 

 the erectile tufts of hair on the hindwings of Mycalesis and of the Morphimv, the raised 

 stripes along the median nervules of the forewing in some species of Argyunis. In 

 the PicriiiiE the sexes almost invariably differ in colour, and the outer margin is more 

 rounded in the females than in the males ; but, with few exceptions, as for instance, the 

 eretile tufts on the hindwings of Catopsilias, there are few prominent external features to 

 distinguish the sexes. In the /'<7;>///t?«/Wie the sexual distinctions, irrespective of colour and 

 outline, are very various. P. polyctor, and some of its allies, have raised stripes along the median 

 nervules of the males, as in Argynnis ; in Leptocircus and in many species of Papilio, 

 such as P. zaleucus, P. nox, and its allies, the abdominal margin of the hindwing is 

 broadly folded back on to the upper surface in the males. In Ontilhoptcra ^ and in some Papil'tos 

 males have a pair of conspicuous corneous valves on the last segment of the abdomen ; while in 

 Panmssius the females are furnished with a corneous pouch on this segment. In Teinopalptis 

 the male has one tail on the hindwing and the female has three. Among the ZTi^j/d'/^V/^?, the 

 only remaining family, the discrimination of the sexes is often a difficult matter. According 

 to Westwood in some groups* the fore-margin (costa) of the forewing is recurved in the males, 

 the enclosed space being thickly clothed with pale coloured down ; in others the males have a 

 large velvety patch near the base of the forewing ; in others the males have a thickened oblique 

 ridge in the middle of the forewing ; and in others the form of the club of the antennae differs in 

 the sexes. In life the females are as a rule less active than the males, and less frequently seen 

 on the wing. It often happens that, v/hen males are common in collections, females are 

 rare or even unknown, as from their more sedentary habits they are more likely to escape 

 observation. 



The powers and style of flight vary much in the different genera, so much so that a prac- 

 tised observer will generally readily distinguish the different genera on the wing. 



The genera in many cases contain a large number of species which can be grouped under 

 several types. Some of the largest of these genera, such as Danais, Eitplcea, Lethe, and 

 Mycalesis have in recent years been divided up into numerous groups, based chiefly, if not en. 

 tirely, on the characters of the male insect. The generic value of these sub-divisions is doubtful, 

 but their usefulness as aids to correct arrangement and identification of the species is unquestion- 

 able. In order to retain the names of these sub-divisions, many of which will probably be 

 adopted as generic divisions in future works, but which at present we do not feel justified 

 in using to the exclusion of the name of the larger and more completely defined group, 

 of which they form sections, we have usually added in brackets after the generic name, the 

 name of the minor group where it has been separately characterised. 



With regard to species and varieties, we have found it convenient to describe, where there 

 is any room for doubt, under its own distinctive name, every form that has been separately 

 characterised. The question whether any particular foim represents a species or a variety of 

 a species can at present be decided in most instances in this country only as a matter of con- 

 jecture, for a knowledge of the life-history in all its stages is essential to the authoritative 

 settlement of such questions ; at the same time the evidently, or apparently allied species, are 

 carefully grouped together, and the nature of the variety is indicated as closely as our present 

 knowledge will allow. 



Exclusively American. 



