Thursday was definitely not ideal butterfly weather- cold and wet –which was a shame after such a beautiful start to May. But a brave bunch of us gathered in the beautiful location of Yarner Woods at the Woodland Centre to meet Megan Lowe from Butterfly Conservation and to learn more about the ecology and field identification of two of our early rare moorland butterflies the pearl bordered and small pearl bordered fritillary
Over the sometimes torrential rain which threatened to drown out all conversation we learned all about butterfly ecology, food plants and identification strategies.
Did you know for example that you can tell whether a butterfly overwinters in its adult form by looking at how knobbly its wings are? Butterflies like the peacock and comma have knobbly wings- therefore they overwinter as an adult!
Also you may know that the latin for butterfly is lepidoptera meaning scaled winged insect but did you know that the scales detach which may help it evade predation by spiders and their webs?
Worryingly we learned that the pearl bordered fritillary has declined in its distribution across the UK by over 95% over the last 200 years and has reduced in its abundance by over 71% over the same time. The story for the small pearl was similarly bleak although it seems to holding on better in Scotland and the north.
These fritillaries traditionally were linked to coppiced woodlands following the woodsman around as he cleared patches of the woodland feeding on the flush of violets. Since the demise of coppicing as an industry this has had a massive impact. What we find now is that the fritillaries are able to use bracken slopes on the moor like micro woodlands and so they are holding on in these areas with the right management.
After our own nectar break to take on tea and sugary flapjacks we focussed on id skills. Both butterflies can be found in early spring- the pearl is first then the small pearl, but there is overlap between the two so being able to tell them apart is an important field skill!
From the top both butterflies look amazingly similar with only subtle differences. In our practice session looking at images of the two species side by side it felt a little like looking at one of those spot the difference competitions you used to get in comics.
From the underside though it became easier to see differences and the reason for the pearl name becomes apparent. On the pearl bordered fritillary there is one white mark in the middle of each wing which does indeed pick up the light like an opalescent pearl. The small pearl has several more( so perhaps should be the “more pearl” rather than “small” pearl)
After lunch there was a break in the weather so we rushed out to see if we could put our new id skills to the test. This was when we realised just how amazing the evolutionary markings and colourings of the underwing is because they pick up perfectly the whites and greens and coppery colours of the unfurling bracken tips where they often rest making themselves almost invisible. With the very wet weather the pearls were taking shelter as best they could tucked under the old bracken or under leaves with only one bravely sheltering high up on a bracken stem for us to find.
And now we know how to spot these rare butterflies which will be on the wing through May and into June we need to put it all into practice and get out and help Megan and the team with their monitoring of the moor!