Members of the Society recently promoted MKNHS at Emberton Country Park as part of its 60th anniversary celebrations. On the Saturday afternoon Jagoda, Linda, Bob and myself were wilting in the heat when we met a very nice family who live nearby in Emberton. A lady with an Hispanic accent (we didn’t ask her name) came into our gazebo with her two young daughters. The children were clearly very enthusiastic about nature and enjoyed seeing our live caterpillars as well as the rocks and plant materials which we had on display. The mother explained that they leave much for their garden wild to encourage wildlife and showed us pictures of some of the dragonflies and butterflies in her garden. She then asked us to identify a couple of caterpillars from her garden. The first of these was a picture of a fully grown Vapourer moth – common enough on a host of trees and shrubs. It was the second photo that left me open-mouthed!
This was a picture of a fully grown, fifth instar larva of Monarch butterfly Danaus plexippus. Most naturalists will be familiar with this as the great migratory butterfly of the Americas, famed for its huge, multi-generational migrations. It does occur in the UK as an accidental migrant – in most years just a few individuals cross the Atlantic and are found in SW England and Ireland. But since the larval foodplant is Milkweed Asclepias spp., a group of plants which do not occur in the UK, the caterpillar is virtually unknown here. In fact, there is just one documented case of breeding from Kew Gardens in 1981, where milkweeds are grown.
So how on earth did a Monarch larva turn up in Emberton village in April 2025? I asked if they had visited a butterfly house (such as the one at Whipsnade) recently but they had not. Is it possible that the specimen had been imported on a plant, either as an egg or young larva? This is probably the most likely origin but few garden centres stock Asclepias. What happened to this specimen? It is tantalising to wonder if it made it through to adulthood, if it had anything to feed on. I really should have asked more questions but did not want to overwhelm the lady and her children! She took one of our leaflets and seemed quite interested in becoming a member – so perhaps we will get the full story in due course. In the meantime, the mystery of the Emberton Monarch remains…
Martin Kincaid
July 2025