Teme Valley Musings, August 2018

by Stephanie Mocroft

Now is the best time of year to see some of Britain’s largest butterflies in flight. One such is the silver-washed fritillary, which I was delighted to spot for the first time this year in our local wood, back at the beginning of July. It is large a woodland butterfly, a striking creature, bright orange with black flecks and a penchant for gliding into sunny woodland glades. Whilst I watched it, its strong straight flight made it seem aloof from the many circling meadow browns, who were also enjoying the sunshine, but busy fluttering at a lower level not far above the woodland floor.

The silver-washed fritillary favours mixed broad-leaved woodland, particularly if it contains oak. On the wing from June to late August the best place to see one is in the Wyre Forest. Altogether there are eight different British fritillary butterflies, five of which live in the West Midlands, and the silver-washed, so-called because of silver markings on the underside of the wings, is the largest of them.

The males are first in flight and they fly at speed along woodland rides on the look-out for potential mates. An elaborate circling courtship display follows, and if a female accepts her suitor, eggs are subsequently laid near to the specific caterpillar food plants. These are dog violet, sweet violet and wild pansy. The eggs are not deposited directly on the plants but in crevices in the bark of nearby trees, often oaks. The eggs hatch and the ensuing caterpillars weave some silk and hibernate until the following spring. On waking they climb down the tree to look for violet leaves to nibble. Once fat and fully developed they climb back up into the tree and hang from a twig transformed as pupae. Once emerged as adult butterflies they sip nectar from the flowers of bramble, thistle and hemp agrimony.

There is good news to report about silver-washed fritillaries because they are doing well at the moment and it is thought that their numbers are higher now than in the past. The high brown fritillary, a rare relative, and the UK’s most endangered butterfly, has been in the news recently, also with good news. It lives in a valley in Devon where counts of over 200 individuals were made early in the season. Researchers put this unexpected abundance down to a long cold winter which held back bracken growth, followed by a warm and sunny June which was ideal for caterpillar development. It’s nice to have a few positive nature stories for once!

Finally, a thought about the name fritillary. It is apparently from the Latin word for dice-box and when used for butterflies and also for the flower, the snake’s-head fritillary, it refers to the chequerboard patterning that they all share. Were Ancient Roman dice-boxes decorated like chequerboards? I don’t seem to be able to find that out!