On Thursday I showed a small butterfly that I saw while taking images for my post about the Slope on Thursday. From a quick look through my Collins Butterfly guide to Britain and Europe (why is it not just Europe, Britain is part of Europe isn’t it?) I had thought it was a Skipper.
But the sharp eyes of my husband identified it as quite a rare visitor, A Geranium Bronze, Cacyreus marshalli.
Geranium Bronze butterfly, Cacyreus marshalli
The Geranium Bronze butterfly (Cacyreus marshalli) is a native of southern Africa, and was accidentally introduced into the Balearic Island of Mallorca, Spain, probably in 1987, and since then it has spread to the other Balearic Islands and other countries in southern Europe. It spread to mainland Spain in 1993, and to the south of France in 1997. By December 2000, it had spread widely within the south of France, and has also been recorded in Italy, Belgium and Morocco.
Biology: The Geranium Bronze occurs on cultivated geranium (Geranium and Pelargonium) species in Europe and can pass through five to six generations per year in Mediterranean locations. The adult butterfly is small and bronze-coloured with a wingspan of about 1.5 to 2.7 cm. The outer margin of the forewings is decorated with white dashes, and there is a white band around the edge of the hind wing. Each hind wing also has a black eyespot and a small ‘tail’.
The small (0.5 mm), yellow-white eggs of the butterfly are laid on buds or on the underside of leaves. After emerging from the egg, the tiny (1 mm) larvae bore into the plant, where they feed and develop. On reaching the third instar, the larvae leave the flower bud by initiating a gallery into the stem. The larvae vary in colour between yellow and green, with stiff white hairs, and sometimes have pink markings along their body.
At 20°C (because this varies with temperature) the larvae complete their development to pupae in about 30 days and the pupal stage lasts about 17 days. The pupae gradually develop a brown mottling and are often found within plant stems, although they also occur on the ground in leaf litter.
Symptoms and detection The damage becomes most visible during the hot season when the larvae are most active. Flower damage is the most visible symptom. Flowers can be totally eaten by the larvae. Damage can be seen on flower peduncles and is often associated with secondary damage by microorganisms which can also colonize the tissue around the entry hole of the larvae into the peduncles. Leaves may be partially eaten by the larvae but this symptom is less frequent and can be confused with feeding by snails. Eggs can be found at the level of flower buds, and less frequently on leaves. Caterpillars are found in flower buds or where they bore into the stem. Entrance holes in buds and stems are easy to detect. Once attacked, the stems become blackish. Others species of Lepidoptera developing on Geraniaceae do not mine in stems.
Dispersal: The potential for natural spread is very low. The flight is short in duration, leisurely and interspersed with frequent rests. The most likely means of international dispersal is the movement of infested plant material, since larvae cannot easily be detected because of their habitat within the stem. Control Examine rooted geranium cuttings when they are brought. Techniques such as propagation via stem cuttings, removal of damaged tissue, deadheading, pinching out of growing-tips and pruning present opportunities to examine plants for signs of infestation. Parts which are infected should be eliminated and treated with insecticides.
The pest has potential to establish in the Mediterranean basin and can be considered as a real danger for the European mainland.
While the pest has a very restricted distribution in Europe, great vigilance is needed to prevent its establishment in new areas. Planting material should be obtained from areas free from the pest. If C. marshalli enters and establishes in an area, it may be very difficult to ensure that nurseries producing pelargonium planting material can be certified free from the pest.
The above was prepared by the Ministry for resources and rural affairs, Malta.
Interestingly I had been given a couple of large Geranium plants about a month ago and I am assuming that eggs or caterpillars were included with the gift! I saw another this afternoon again nectaring on Rosemary flowers.
I is very satisfying to have a mystery resolved.
Creating my own garden of the Hesperides 
Glad you identified this one. That is too bad that it can infest your geraniums. Here the introduced Cabbage Whites decimate my cabbage family crops so I have to grow them covered.
Cabbage whites damage all brasicas here too, although this year there is an even worse pest which I must photograph and write about soon. At least I can see and squish the eggs and caterpillars of the CW.
Sad that it is so destructive because it is so beautiful. That is a lovely shot of it. It looks as if it is posing for you and has chosen a flower that shows it off to perfection. Your brassica bugs are beautiful too but I would be ruthless with them. But I think I would be happy to see your lovely butterfly even if it did eat my geraniums.
I don’t think just one or two butterflies are going to cause too much problem (famous last words maybe!). I only have a couple of scented leaved geraniums not a huge collection of flowering ones that many people have here.
I’ve never seen this beautiful butterfly in France. I cannot quite decide whether to be sad or happy as I like my geraniums 😕 Amelia
I don’t think it will prove to be a major problem yet to gardeners but something to watch for; As the butterfly itself is so small I imagine the caterpillar is equally small.
It is good to know what it is, and to be aware of the damage it can cause too! It’s a shame that such a pretty creature is seen as a pest just because it got transported far from home by mistake. Glad you managed to identify it.
The globalization of plants (and everything else) isn’t always a good thing. At the moment there don’t seem to be a huge number in Europe but if numbers increased significantly it could change what we grow; the lily beetle has stopped many people growing lilies which is such a shame when they are so beautiful. In a commercial situation they must have some control I would have thought.
Love the photo and the background information was really important…This is how I learn a lot about the creatures in my garden.
Glad you enjoyed the post Charlie.
I am glad you have identified your beautiful butterfly Christina. I would sacrifice a few pelargoniums for her.
It should of course be called Pelargonium Bronze, I don’t think it feeds on hardy geraniums.
A beautiful creature with an intriguing name, Geranium Bronze. Congrats to your husband for identifying the little pest.
He’s very good at picking out the important features for an ID, I tend to get side-tracted by the pattern rather than the fact it has a long tail etc.
That’s a gorgeous photo. Too bad it’s a butterfly that will potentially wreak havoc in the geranium industry. With globalization, we’ve all been faced with unwanted pests, introduced through similar means and without a common predator. Good luck with your plants.
It is hard to imagine that something so small and innocent looking can cause such damage, but perhaps it says more about the way we produce plants than about the pest itself.
So will you be on the lookout for caterpillars or are you going to let them go their own way? I don’t mind cabbage whites (well not too much) but I think I would be more ruthless with a geranium pest.
Will check the geraniums but I can’t see it being a major problem.
It is a lovely butterfly with such velvety wings. Too bad it is a pest! I hope all goes well with your geraniums and other plants.
Don’t worry, I don’t have enough geraniums to make it a problem in my garden. I can see it would be a major problem in a glass house where you were producing geraniums commercially.
What a treat! Never saw one of those but with my newly planted geraniums I might still get the chance. Thanks for introducing me to it.
Maybe we should hope that you don’t see any.
I sometimes get carried away as I don’t think of creatures as pests usually (nasty word too) but I get the message and know what you mean. I’m just intrigued by the diversity and beauty of animals. 😉 mea culpa
I don’t usually think in terms of pests; I think the problem with my post is that I used a website that percieved them to be serious pests, I’m not so sure they are (at least not yet).
Interesting to know. I’m glad your husband solved the mystery for us all!
He’s good at identifying birds as well; I should be like others who have interesting names for their husbands; I particularly like Cathy’s (words and herbs) “man of many talents”. The only thing I’ve come up with so far is rather long “my man who (thinks he) knows everything”.
He would like it better if you added just a few more words! “…and probably does.” LOL
Very true!
Very satisfying to have identified your mysterious visitor, though perhaps this isn’t the time to begin establishing a large collection of scented pelargoniums… I am slightly amused that they munch both sorts of geranium! I knew I was starting to be a gardener when I realised the difference between them.
I think it must have arrived on the geraniums I was given, although there isn’t any obvious signs that they’ve been munched!
they are in my garden, but I have enough vast pelargonium bushes, that we can share. And some caterpillars are going to the birds for their fledglings.
Life is different if you have a row of windowboxes on your balcony, which are no longer filled with pelargoniums. But there are other flowers to enjoy …
I’m a great believer of balance in the garden; I never use chemicals, I hand pick off eggs and caterpillars of the cabbage white (they aren’t prepared to share but would take the whole crop). I posted all the information only because it was a new butterfly to me, I can’t believe it will be a big problem in my garden but I will look for the caterpillars regularly. What varieties of birds take them in your garden.
I confess I’m not patient or observant enough to say which birds take those caterpillars. But weavers, sparrows, red bishops, Cape robins, sunbirds – they are all busy collecting bugs for babies.