Fritillaries legs

[Trev Sawyer]

Hi Guys,
Odd question for you. I know that male Duke of Burgundy butterflies have only 4 legs, whilst the females have the normal 6, but what of the true fritillaries? The reason I ask is that I have recently been taking photos of various frits and on one or two shots, it appears that some have only 4 legs. I have noticed that on occasions, fritillaries will walk/stand on 4 legs, whilst keeping the front pair of legs, tucked away. These front legs appear shorter than the other legs.
Oddly, in some snaps it appears that BOTH members of a mating pair of frits have only 4 legs, but I'm sure this is not true. It must be the way at least one of the pair stands.
Also, if males of some butterflies emerge with only 4 legs, this situation must have been selected out by evolution over many generations as "beneficial" (there must be an advantage in having less legs). Any theories as to what the benefits may be? Is it easier for them to "get their legs over" so to speak, if there are only 2 rather than 3 on each side

Trev

[Dave McCormick]

Not sure if this helps, doubt it but, nymphalidae, 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 fore legs is considerable, e.g. Danainae and Satyrinae In many of the forms of these subfamilies the fore legs are kept pressed against the underside of the thorax, and are in the male often very inconspicuous.

[Padfield]

I vaguely remember reading that the 'brush feet' are sense organs. Perhaps they are used for detecting aerial food traces and scents, as the front feet of other butterflies are used for testing food. I too would welcome more information on this.

Guy

[Dave McCormick]

Brush footed: In adult butterflies, the first pair of legs are small or reduced, giving the family the other names of four-footed or brush-footed butterflies.