Dark Green Fritillaries in an Undiscovered Dale.

I think this blog may be developing into a celebration of seasonal natural spectacles posted just a little too late for the reader to actually go out and enjoy them. Speaking of which, on the first of July, I visited, in the company of the Bee Girl, and a dear friend and Londoner with whom I studied Environmental Science in the capital, one of the less-visited Dales of the southern Peak District, in pursuit of a rather special butterfly.  

The Dark Green Fritillary is an unfamiliar butterfly to many of us, although it is probably the commonest large fritillary in the British Isles. I first met it, when, during a heatwave not dissimilar to this one, I was studying the Northern Brown Argus at Warton Crag in Lancashire. The adults were on the wing for a few days, until, in the words of the site’s RSPB warden “they melted in the heat.” I’d only seen the odd one or two to date, mostly in Cumbria, so when a member of local Natural History group on a popular social network reported counting 40 or so on the footpath into Long Dale and Gratton Dale, just off the Via Gellia, about fifteen minutes from my home, it seemed an opportunity not to be missed. We’d been running about for the past few days, finding the Londoner her first Dipper at Lathkill Dale and connecting with Treecreepers and Stone Circles on the Eastern Moors, so an evening visit turned out the best we could manage. We went with some apprehension that the advancing hour would preclude success, but our fears were unfounded. 

We were greeted just a hundred metres or so from the layby, by a single Dark Green fritillary. Its topside was a rich burnt orange orange in the high midsummer sun, intricately marked with blacks and browns, and when it closed its wings, the underside, which gives the species its name, was a deep pastel mid-green, jewelled in silver, lustrous and metallic when caught by the sun. A beautiful insect, bigger than a Comma, it was comparable in size to a Peacock or a Red Admiral. Walking a little further down the dale, we were surrounded by dozens of these magnificent insects, bright, fresh orange individuals, and more faded specimens bleached a little by a few days in the sun.  Big, bright males maintained small territories, chasing off any rival males which dared to nectar at their Thistles or deep purple Knapweed flowers, and would eagerly drive off any passing Meadow Browns or Ringlets, which were abundant, occasionally appearing even to fly directly at human observers, before swiftly changing course to pick their battles. One even hassled a large Aeshnid dragonfly.

Dark Green Fritillaries fly from late June until late July, reaching a peak in mid July, though the anecdotal evidence of the warden at Warton Crag suggests hot weather can shorted this flight period. They are univoltine, and overwinter as a young larva, eating only their own eggshell before entering hibernation, miniscule and vulnerable, among the decaying vegetation. In spring the larvae emerge to feed on the leaves of violets. The larvae are black and as they near maturity broadly resemble those of the large nymphalini.

The Dales had more surprises still.  Butterflies on the wing included vibrant Common Blues (Polyommatus icarus), a small cluster settling down to a communal roost, and more than a few of the local, univoltine race of Brown Argus (Aricia agestis), long considered Northern Brown Argus (A. artaxerxes) distinct from strikingly similar female Common Blues by a single missing spot on the forewing at rest.  The Bee Girl found Small Heath, (Coenonympha pamphilus) a small and unassuming, and particularly fluffy looking satyrid butterfly of the grasslands, thought to be a declining species.  Plenty of Burnet Moth (Zygaena spp.) were on the wing, as were a whole host of common butterflies, we counted 12 species in all.

Brown Argus (Aricia agestis) 

Though many of the grassland and scrubland birds have finished breeding by July and largely gone to ground, there were still a few about. The bushes were alive with fledgeling Willow Warbler, and a single hen Redstart was noted, darting away, a fleeting glimpse of that tell-tale orange tail for which the bird is named.  We heard a Raven cronking but unfortunately it did not reveal itself. Swallow fledglings with short streamers wheeled overhead and a single Brown Hare paused on the rocks above to look down at us with suspicion. These dales are stunning on a summers’ day and that day, the butterflies were the stars.  We walked out of the dale at about 8pm, and still the Fritillaries were active, busy and chasing.