Monday 15 May 2023

Silver-washed Fritillary Mystery.

One of my strangest butterfly finds happened on Saturday when Lisa and I visited Tugley Woods in Surrey. The idea of the visit was to do a recce for my Naturetrek tour later this week, basically to see if the Wood White was on the wing yet.

More of that in a future blog, but there we were strolling along the rides when a large brown butterfly flew towards us and landed high up a tree and started to feed on the nectar. I quickly got the binoculars on the butterfly and almost fell over in surprise, as it was a female Silver-washed Fritillary. This is a butterfly of the high summer, and shouldn't be on the wing for another 6-8 weeks. It was also clear that this was not a fresh individual, and was almost certainly at least 10 days old.

Many questions and theories abound when something like this happens. The most obvious thought is that it is a home reared individual that has been brought through far too early and whoever reared it has let it go in a wood where the species is prevalent in the summer. However, over the past few years several single brooded butterflies have managed to produce a few 2nd brood individuals. Species that come to mind are Duke of Burgundy, Orange-tip and White Admiral. Just maybe, this Silver-washed Fritillary, instead of hibernating as a 1st instar larva like it should do, decided to feed up and then hibernated as a much later stage larva, pupa or even as a butterfly. This is unlikely, but in nature anything is possible, especially with the warming climate. 

One more observation that perhaps gives more credence to this theory is that a butterfly enthusiast in Somerset who was doing a butterfly transect saw what he was pretty sure was a Silver-washed Fritillary, but didn't get a clear enough view to be absolutely sure. This was on April 28th, which looking at the condition of our specimen, could have been on the wing around that time. So maybe our Silver-washed Fritillary isn't the only one flying around. I guess we will not know what has really happened unless someone comes forward saying they released the butterfly, or in future years more of these out of season Fritillaries are seen.

The butterfly expert Matthew Oates also hasn't ruled out the possibility that the long hot summer of 2022 could have created different behaviour that could have produced this strange event.

Fortunately, both Lisa and myself managed to get some photos of this strange sighting, although because she had her telephoto camera out already, and I had to rummage through my bag, she managed to get more shots, and better shots than I did in the brief moments before it flew. Over the next 30 minutes we saw the butterfly several more times, but always in flight.

Female Silver-washed Fritillary.

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