Common Geranium Bronze

EASY GARDEN BUTTERFLIES

Common Geranium BronzeCacyreus marshalli

The Common Geranium Bronze is one of the Lycaenidae (Gossamer-winged Butterflies), subfamily Polyommatinae (Blues, Bronzes etc.). Blues are tiny to small butterflies, many of which have brilliant blue uppersides (although some are dull grey or brown). Common Geranium Bronze is one of the brown ones.

The male Common Geranium Bronze’s wingspan is 15-23 mm, the female’s, 24-27mm. The sexes are alike. There are two less common similar species. One is the Water Geranium Bronze Cacyreus fracta which has some violet-blue on the upperside. It lives in wetlands in cooler areas like the Western Cape and the Drakensberg. The other is Dickson’s Geranium Bronze Cacyreus dicksoni whose upperside is more of a coppery hue – and is found in the Karoo.

They fly quite low, fluttering among the vegetation and are often seen along herbaceous borders. They keep close to the host plants.

Both sexes are fond of flower nectar. Males also like to sit on damp earth and mud, sucking up dissolved minerals.

Distribution

The Common Geranium Bronze is naturally found in most areas of South Africa except the most arid parts of the Desert and Karoo. However, it’s become a cosmopolitan butterfly. South African Geraniaceae have been exported extensively to Europe. At some point some caterpillars, eggs or pupae went along for the ride. Now it’s found as far afield as England and has caused a lot of trouble in the pot plant trade in places like Spain.

Fortunately, its natural predators keep its numbers in check here at home. We can enjoy it as a charming little garden butterfly.

Egg

The female Common Geranium Bronze lays her tiny, pale blue-green eggs singly on buds and leaves of the host plant. They are about 0.3mm diameter by 0.5mm high. They are flattened discs, with many tiny moles connected by cross-ribs, creating indentations. The eggs turn white as they mature. The egg stage lasts about six to eight days.

Caterpillar

Common Geranium Bronze caterpillars are small and slug-shaped, as are most caterpillars of the Lycaenidae. This species has bristly hairs on its back. They feed on flower buds, seeds, and young shoots of the host plants, later on boring into the stems. They often hide under leaves lying flat on the ground. They grow from 1mm to 13mm long in three moults over a month. They vary greatly in colour from green to yellow, with a varying extent of red or pink markings. They do not have a ‘honey gland’ like some other members of the family do.

Pupa/Chrysalis

Common Geranium Bronze pupae are elongated and very hairy. They are attached to a silken pad spun by the larva on a dead leaf or piece of debris by tiny hooks on the tail in a manner similar to ‘Velcro’, with a silken girdle around their ‘waist’. They vary in colour from pale green to yellow or brown, with darker brown mottling and pale pink bands. They are about 8-9mm long. The adult normally emerges in about two to three weeks.

Host plant

Common Geranium Bronze caterpillars feed on many species of Pelargonium and Geranium. These plants are widespread in the wild in South Africa and are very popular with gardeners. Pelargoniums are particularly showy, and some gardeners view this butterfly as a pest because its larvae sometimes bore into the plants’ stems. This can stunt their growth, but sometimes you need to make a little sacrifice to have butterflies in your garden!