Fam. Papilionidae.
4. The front legs are like the other pairs; their tibiae however possess pads; the claws are small, toothed at the base, and there is an empodium; the metanotum is concealed by the prolonged and overhanging mesonotum.
Fam. Hesperiidae.
The relations between the families Erycinidae, Lycaenidae, and Nymphalidae are very intimate. All these have the front legs more or less modified, and the distinctions between the families depend almost entirely on generalisations as to these modifications. These facts have led Scudder to associate the Lycaenidae and Erycinidae in one group, which he terms "Rurales." It is however difficult to go so far and no farther; for the relations between both divisions of Rurales and the Nymphalidae are considerable. We shall subsequently find that the genus Libythea is by many retained as a separate family, chiefly because it is difficult to decide whether it should be placed in Erycinidae or in Nymphalidae. Hence it is difficult to see in this enormous complex of seven or eight thousand species more than a single great Nymphalo-Lycaenid alliance. The forms really cognate in the three families are however so few, and the number of species in the whole is so very large, that it is a matter of great convenience in practice to keep the three families apart. It is sufficient for larger purposes to bear in mind their intimate connexions.
The Papilionidae and Pieridae are treated by many as two sub-divisions of one group. But we have not been able to find any justification for this in the existence of forms with connecting characters. Indeed it would, from this point of view, appear that the Pieridae are more closely connected with the Lycaenidae and Erycinidae than they are with Papilionidae; in one important character, the absence of the pad of the front tibia, the Nymphalo-Lycaenids and the Pierids agree. It has also been frequently suggested that the Papilionidae (in the larger sense just mentioned) might be associated with the Hesperiidae. But no satisfactory links have been brought to light; and if one of the more lowly Hesperiids, such as Thanaos, be compared with one of the lower Papilionidae, such as Parnassius, very little approximation can be perceived.
It appears, therefore, at present that Hesperiidae, Papilionidae, Pieridae, and the Nymphalo-Lycaenid complex are naturally distinct. But in the following review of the families and sub-families of butterflies, we shall, in accordance with the views of the majority of Lepidopterists, treat the Lycaenidae and Erycinidae as families distinct from both Nymphalidae and Pieridae.[[212]]
The number of described species of butterflies is probably about 13,000; but the list is at present far from complete; forms of the largest size and most striking appearance being still occasionally discovered. Forty years ago the number known was not more than one-third or one-fourth of what it is at present, and a crowd of novelties of the less conspicuous kinds is brought to light every year. Hence it is not too much to anticipate that 30,000, or even 40,000 forms may be acquired if entomologists continue to seek them with the enthusiasm and industry that have been manifested of late. On the other hand, the species of Rhopalocera seem to be peculiarly liable to dimorphic, to seasonal and to local variation; so that it is possible that ultimately the number of true species—that is, forms that do not breed together actually or by means of intermediates, morphological or chronological—may have to be considerably reduced.
In Britain we have a list of only sixty-eight native butterflies, and some even of these are things of the past, while others are only too certainly disappearing. New Zealand is still poorer, possessing only eighteen; and this number will probably be but little increased by future discoveries. South America is the richest part of the world, and Wallace informs us that 600 species of butterflies could, forty years ago, be found in the environs of the city of Pará.
Fam. 1. Nymphalidae.—The front pair of legs much reduced in size in each sex, their tarsi in the male with but one joint, though in the female there are usually five but without any claws. Pupa suspended by the tail so as to hang down freely. We include in this family several sub-families treated by some taxonomists as families; in this respect we follow Bates, whose arrangement[[213]] still remains the basis of butterfly classification. With this extension the Nymphalidae is the most important of the families of butterflies, and includes upwards of 250 genera, and between 4000 and 5000 species. There are eight sub-families.
It is in Nymphalidae that the act of pupation reaches its acme of complication and perfection; the pupae hang suspended by the tail, and the cremaster, that is the process at the end of the body, bears highly-developed hooks (Fig. 177, C, D). The variety in form of the chrysalids is extraordinary; humps or processes often project from the body, making the Insect a fantastic object; the strange appearance is frequently increased by patches like gold or silver, placed on various parts of the body. It is believed that the term chrysalid was first suggested by these golden pupæ. The Purple Emperor, Apatura iris, differs strikingly in the pupa as well as in the larva-stage from all our other Nymphalids; it is of green colour, very broad along the sides, but narrow on the dorsal and ventral aspects (Fig. 177). The skin of this pupa is less hard than usual, and the pupa seems to be of a very delicate constitution. The Purple Emperor, like some of the Satyrides as well as some of its more immediate congeners, hibernates in our climate as a partially grown larva and passes consequently only a very brief period of its existence in the form of a pupa.