Geranium Bronze

Cacyreus marshalli (ka-SY-ree-uss mar-SHALL-eye)

Geranium Bronze - imago - Thatcham - 15-Oct-06 (0820) [REARED]
Photo © Pete Eeles

Checklist Number

Family:LycaenidaeLeach, 1815
Subfamily:PolyommatinaeSwainson, 1827
Tribe:PolyommatiniSwainson, 1827
Genus:CacyreusButler, 1898
Species:marshalliButler, 1898

< Previous SpeciesNext Species >


This South African species, considered a pest of cultivated Pelargoniums and Geraniums, first arrived in the British Isles in 1997 when an individual was seen flying around Geraniums in a garden in Kingston, Lewes, East Sussex. Immature stages were subsequently found that gave rise to another generation. It is believed that this butterfly was accidentally imported as immature stages in Geranium plants. This butterfly was accidentally introduced first to the Balearic Islands in 1987 and has since spread to much Spain, France, Italy, Morocco and has even reached Malta.

The following text was kindly provided by, and is copyright, Crispin Holloway, and many of the photos on this page are from Crispin's father, John.

Geranium Bronze (Cacyreus marshalli) was first recorded in Britain by my father (John Holloway) in Kingston, Lewes, East Sussex on the 21st Sept 1997. This was the first new species to be recorded in Britain for 80 years. I remember it all very well. It is probable that it was introduced in the form of ova or young larvae on our neighbour's plants bought from a nursery. It is thought the plants were imported from Spain or Portugal early in the year. When the nursery found out why everyone was wanting to know where their Geranium came from, their story changed a few times - they probably did not want to be thought of as being responsible for introducing the species. The Geranium Bronze (Cacyreus marshalli) is a South African Lycaenid whose larvae feed on Geranium and Pelargonium. It was accidentally introduced to the Balearic Islands in about 1987 and has since spread to much of Spain, southern France, parts of Italy and Morocco. Articles appeared in Butterfly Conservation Sussex Branch Newsletter Winter 1997, Butterfly Conservation News No. 67, Atropos No. 4 & 6 as well as all the local and some national media.

This is how it all started: At first glance it was thought to be a Brown Argus behaving strangely, flying round the Geraniums in the front garden - then the tails on the hind wings were noticed. My father first thought it was a Lang's Short Tailed Blue. He took a number of photos and video, it was very approachable to within about six inches then we saw it was ovipositing on the potted geraniums! We were completely puzzled. Nick Bowles described a picture of Geranium Bronze (Cacyreus marshalli) to my father and we were then able to confirm that it was a Geranium Bronze.

Two days later (23/9/97) we saw and photographed a second individual (the first one had scratch marks on a wing, but this one hadn't); it continued to flutter around and laid more eggs. Then a third appeared. This one was not interested in geraniums, it was smaller, darker and had more distinct markings - probably a male. On one day we had about 4 flying in the garden!

We searched all the Geranium and Pelargonium and found many eggs. We then chose to rear them in different ways - some on potted plants covered in netting at room temperature in the house, and some in small plastic containers indoors and some on plants in the greenhouse. The eggs hatched in 6 days.

Most of the young larvae burrowed into the flower buds but a few mined the leaves initially, later scaling the underside of the leaf. They were difficult to rear in the plastic containers, only feeding on old dried flower buds and leaves - even when fresh food was put alongside them they still went for the old dried up stuff. Those in warm situations grew more quickly than those on plants in an unheated room.

In South Africa the lifecycle is about 46 days. Our first larvae pupated 52 days after hatching from the egg. With great difficulty we managed to get a larva to feed on Dove's-foot Crain 's-bill. It fed very slowly for several weeks then perished. I think it is very unlikely that it would ever adapt to feeding on this plant as they would really struggle, regardless of the cold.

We had several visits from MAFF to assess the potential of the species as a threat to the horticultural trade. With the flourishing horticultural trade it is quite possible some more could come into the country but I think it is unlikely that it could ever survive our winters, especially as it is continually brooded. Having said that, on Nov 1st 97 we did find one female roosting in the garden with a Small Copper after an air frost of -1.8c. The story ends with one surprise sighting the next May 1998 - it is presumed to have made it through the winter feeding in our neighbour's greenhouse.

Cacyreus marshalli

This species was first defined in Butler (1898) as shown here and as shown in this plate (type locality: South Africa).

Geranium Bronze - Alpes-Maritimes - 18 October 2012

Photo © CFB

Geranium Bronze - imago - Thatcham - 15-Oct-06 (0815) [REARED]

Male Underside
Photo © Pete Eeles

Geranium Bronze female - Peasmarsh, East Sussex 31-Aug-2013 [Gordon Jarvis]

Photo © Gordon Jarvis

Geranium Bronze - female - Thatcham - 14-Oct-13 (1) [REARED]

Female Underside
Photo © Pete Eeles

Photo Album ...

Conservation Status

No conservation action is relevant for this species.


Description to be completed.


2. Adventive

This species is considered an adventive, which is a species which arrives in the British Isles with the direct assistance of an external vector, without which it would not be present. Adventives are species that one would not expect to find in this country, either through inadvertent migration or through any other natural means of dispersal, with the exception perhaps of the most extreme meteorological event or possibly the transportation of a stage in the life cycle in a highly unlikely but natural means (e.g. an ovum or larva being transported upon the foot, bill, or plumage of a migratory bird).

Life Cycle

Description to be completed.


Despite being considered a pest, the adult butterfly is quite beautiful. The two sexes are similar in appearance, having chocolate-brown uppersides with distinct chequered fringes and which contrast with the highly-patterned undersides. Adults also have substantial tails on their hindwings, along with a nearby eye spot, which diverts attacks from birds and other predators away from the critical body parts.

Description of nectar sources to be completed.

Photo Album ...


The white, sea urchin-shaped eggs are laid singly on the foodplant, often on a flower bud.

Geranium Bronze - ovum - Lewes, Sussex - Unknown date [John Holloway]

Photo © John Holloway

Geranium Bronze Ovum - Sorrento - Italy - 24-08-11

Photo © William

Photo Album ...


The young larva typically burrows into a developing flower bud, where it scoops out the contents before moving onto another bud. More mature larvae feed more-openly on the outside of the flower buds and will eventually feed on leaves of the foodplant, where they have a preference for older and drier leaves.

The mature larva is noticeably hairy and its green colouring, often with suffused pink stripes running down its length, can make it difficult to find on the food plant.

The primary larval foodplants are Geraniums (various) (Geranium spp.) and Pelargoniums (various) (Pelargonium spp.).

Geranium Bronze Larva - Sorrento - Italy - 25-08-11

Photo © William

Geranium Bronze - larva - Thatcham - 21-Oct-08 (1) {REARED}

Photo © Pete Eeles

Geranium Bronze - larva - Lewes, Sussex - Unknown date (2) [John Holloway]

Photo © John Holloway

Geranium Bronze - larva - Lewes, Sussex - Unknown date [John Holloway]

Photo © John Holloway

Photo Album ...


The pupa is formed on or near the foodplant, or in nearby debris such as a withered leaf, attached by a silk girdle and the cremaster. Like the larva, the pupa is noticeably hairy.

Geranium Bronze - pupa - Thatcham - 10-Sep-06 (0794) [REARED]

Photo © Pete Eeles

Geranium Bronze - pupa - Thatcham - 29-Oct-08 (1) {REARED}

Photo © Pete Eeles

Geranium Bronze - pupa - Thatcham - 29-Oct-08 (2) {REARED}

Photo © Pete Eeles

Geranium Bronze - pupa - Thatcham - 10-Sep-06 (0795) [REARED]

Photo © Pete Eeles

Photo Album ...


Description to be completed.

Click here to see the aberration descriptions and images for this species.

Similar Species

No similar species found.


Watch Video
Watch Video

The following links provide additional information on this butterfly.


The species description provided here references the following publications:

Butler (1898) Butler, A.G. (1898) Proceedings of the general meetings for scientific business of the Zoological Society of London.
Leach (1815) Leach (1815) In Brewster: The Edinburgh Encyclopaedia.
Swainson (1827) Swainson, W. (1827) A Sketch of the Natural Affinities of the Lepidoptera Diurna of Latreille. The Philosophical magazine : or Annals of chemistry, mathematics, astronomy, natural history and general science.