The Nymphalidae are the largest
family of
butterflies, with more than 6,000 species distributed throughout most of the world. Belonging to the superfamily
Papilionoidea, they are usually medium-sized to large butterflies. Most species have a reduced pair of forelegs and many hold their colourful wings flat when resting. They are also called brush-footed butterflies or four-footed butterflies, because they are known to stand on only four legs while the other two are curled up; in some species, these forelegs have a brush-like set of hairs, which gives this family its other common name. Many species are brightly coloured and include popular species such as the
emperors,
monarch butterfly,
admirals,
tortoiseshells, and
fritillaries. However, the under wings are, in contrast, often dull and in some species look remarkably like dead leaves, or are much paler, producing a
cryptic effect that helps the butterflies blend into their surroundings.
Nomenclature
Rafinesque[1] introduced the name Nymphalia as a subfamily name in diurnal Lepidoptera. Rafinesque did not include Nymphalis among the listed genera, but Nymphalis was unequivocally implied in the formation of the name (Code Article 11.7.1.1). The attribution of the Nymphalidae to Rafinesque has now been widely adopted.[2]
In the adult butterflies, the first pair of legs is small or reduced,[3] giving the family the other names of four-footed or brush-footed butterflies. The
caterpillars are hairy or spiky with projections on the head, and the
chrysalids have shiny spots.
The
forewings have the submedial vein (vein 1) unbranched and in one subfamily forked near the base; the medial vein has three branches, veins 2, 3, and 4; veins 5 and 6 arise from the points of junction of the discocellulars; the subcostal vein and its continuation beyond the apex of cell, vein 7, has never more than four branches, veins 8–11; 8 and 9 always arise from vein 7, 10, and 11 sometimes from vein 7 but more often free, i.e., given off by the subcostal vein before apex of the cell.[4]
The
hindwings have internal (1a) and precostal veins. The cell in both wings is closed or open, often closed in the fore, open in the hindwing. The dorsal margin of the hindwing is channelled to receive the abdomen in many of the forms.[4]
The
antennae always have two grooves on the underside; the club is variable in shape. Throughout the family, the front pair of legs in the male, and with three exceptions (Libythea, Pseudergolis, and Calinaga) in the female also, is reduced in size and functionally impotent; in some, the
atrophy of the forelegs is considerable, e.g., the
Danainae and
Satyrinae. In many of the forms of these subfamilies, the forelegs are kept pressed against the underside of the
thorax, and are in the male often very inconspicuous.[4]
Systematics and phylogeny
The
phylogeny of the Nymphalidae is complex. Several
taxa are of unclear position, reflecting the fact that some
subfamilies were formerly well-recognized as distinct families due to insufficient study.
The trait for which these butterflies are most known is the use of only four legs; the reason their forelegs have become vestigial is not yet completely clear. Some suggest the forelegs are used to amplify the sense of smell, because some species possess a brush-like set of soft hair called
setae, which has led researchers to believe the forelegs are used to improve signaling and communication between the species, while standing in the other four. This ability proves useful in terms of reproduction and the overall health of the species, and it is the leading theory so far.[7]