Species: Gonepteryx rhamni
Common names: Brimstone, Brimstone Butterfly, Common Brimstone
Adult Males: Viewed from above (dorsal side) wings are mostly butter-yellow in colour and are iridescent. There is a pair of small, orange spots on the forewings and a larger pair on the hindwings. Viewed from below (ventral side) the underwing is tinged with more green and is less yellow.
Adult Females: Dorsal side, wing colour is greener than in males and lacks iridescence. Ventral side, the underwing is much paler and can look almost white.
Both sexes rest with their wings closed. Underwing wing veins are distinctly raised, having evolved to simulate the leaf veins amongst which the butterfly will hibernate during cold weather.
Wingspan from tip to tip is 60mm to 74mm.
Pupae (chrysalides) are pale green and are extremely well camouflaged as they hang from Buckthorn leaves. They darken over time, mimicking the leaves. Chrysalides are between 22mm and 24mm in length.
Larvae (caterpillars) are green, darkening as they grow to match their foodplant. They are sparsely covered in short, fine, dark hairs. It is common for larvae to 'arch' themselves along a leaf's midrib. Typically length is up to 35mm when fully fed.
Eggs are bottle shaped and are approximately 1.3 mm long. They are greenish-white when laid, gradually darkening to yellow and on to brown as they mature.
Habitat and Distribution
Damp woodlands, sunny paths and rides, scrubby grassland, parks and gardens throughout temperate Europe, Asia and northern Africa. Adult butterflies are very mobile and are seen in low numbers over large areas in many different environments. They have a readiness to search locally for seasonally appropriate food, shelter and breeding grounds.
Gonepteryx rhamni (Common Brimstone) is one of the first butterflies to be seen flying during early spring. These individuals have overwintered as adults, having hatched from eggs laid during the previous summer. Males usually awaken on the first warm day of spring, a few days afterwards the females will join them.