Brimstone, Gonepteryx rhamni
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Identification
Medium to large sized: wingspan, 60 mm.
Males are a bright yellow on both surfaces of both sets of wings. There is a small yellow-brown spot in the centre of each wing; those on the underside of the hind wings being the most conspicuous having a darker outer margin and a paler centre.
Females are much paler, almost off-whitish, with a greenish tint. The Brimstone's wings are characteristically shaped with a bluntly hooked forewing and an abbreviated tail on the hind wings.
Behaviour and life history
The Brimstone is a species of the woodland edges and hedgerows where it spends much of its time flying up and down searching for a mate, in spring, or sources of nectar at other times. It settles for quite a time once it finds a good food source. It is particularly attracted to teasels and thistles. The butterfly overwinters as an adult hidden away in dense evergreen foliage such as Ivy. It makes an early appearance in the spring and lays its eggs in May and June on Alder Buckthorn, Frangula alnus. Larval development is completed by mid July and, after a short pupation, adults hatch from late July onwards.
Where to look for it
As one of the earliest butterflies on the wing, this distinctive butterfly is most commonly associated with woodland edges and hedgerows but it can roam anywhere and is not uncommonly seen in gardens and built up areas. Particularly good sites for observing this species are the rides and woodland margins of Efford Marsh, Forder Valley and Bircham Valley Local Nature Reserves.
Distribution and status
Common and widespread throughout the city.
When to look for it
It is particularly plentiful during warm days in early spring from March onwards. A second population peak is commonly observed in August.
Similar species
The Brimstone can only really be confused with the Clouded Yellow, Colias croceus, but can be easily separated by it wing shape.