This finely-coloured and beautiful butterfly resembles the English
Brimstone, but is quite a distinct variety, being of squarer form and
having no decided point at the angle of the hind-wings. It is peculiar
to the Islands. The male is a most brilliant sulphur yellow, the
fore-wings being of a deeper shade than the hind ones. The hind-wings
have a deep orange spot about the centre. The female differs from the
male in being of a much paler shade of yellow, with quite a tinge of
green all over it; it also has a small orange spot on the fore-wings in
addition to that on the hind-wings. Both wings have red markings round
them on the outer edge, which form an almost interrupted fine line of
colour. The underside resembles the upper, but is paler. The antennæ
are short and thick, with a reddish tinge, which becomes deeper at the
knob.
It is found from January to June in most localities on and at a little
distance from the coast; gardens and fields seem somewhat favoured,
but it is by no means common anywhere. There seem to be several broods
between the months mentioned above, but the larva and pupa have not
been observed.