After a half a dozen or so marsh fritillary butterflies were first recorded on 26th May 2017, it was really encouraging to see them in greater numbers in 2018. In the same part of the reserve it was estimated that up 50 individuals could have been present. Thinking that there was a chance they may have laid eggs a search for caterpillars was made this spring with Tim Bernhard a butterfly enthusiast from Natural England. We walked across an area the size of half a Football pitch and saw at least one hundred caterpillars on our walk. This indicated a really healthy population of caterpillars. Interestingly their main foodplant, Devil’s-bit scabious, was only present in very small numbers, and closer inspection revealed that they were munching the basal leaves of young small scabious plants. This is great news as small scabious is abundant and widespread across the reserve chalk grasslands and suggests that this population arrived from neighbouring Porton Down, where they are already known to thrive on small scabious.
Marsh fritillary butterflies were first recorded in 2019 by volunteer research scientist Stuart Corbett on 13 May around a chalk butterfly bank on one of his invertebrate surveys. I went out to the caterpillar area the following day and had the privilege to witness the emergence of hundreds of marsh fritillaries. The ground was alive with fluttering of the butterflies with their characteristic shiny black netting on orange and custard check. At one point I knelt down in an attempt to choose one to photograph and a chain of seven fighting butterflies passed over my shoulder. I can only imagine that the females had just emerged and one was being chased by a bunch of ardent suitors battling for her attention. Marsh fritillaries were seen far and wide across the reserve in the following weeks, and hopefully we shall see many of the protective webs made by freshly hatched caterpillars around their foodplants later this coming August and September.