Butterflies

The diversity of our valley’s wildlife was well illustrated by searches for butterflies I made during July and August in Lower and Upper Wharfedale. In late July I conducted a Wider Countryside Butterfly Survey on either side of the river below Harewood, as I have done for the last nine years.

As ever, the important factors in seeing butterflies in numbers were sunshine and flowering plants, the key ones in this area being an abundance of thistles, knapweed, ragwort and a few bramble patches still in flower.

I was quite glad that there were less white butterflies than I had seen in some years for they can be remarkably reluctant to settle making it difficult to distinguish between small and green-veined whites. Their small numbers were compensated by two dozen each of ringlets, meadow browns, gatekeepers and small tortoiseshells, the last recently emerged with 14 of them on one patch of flowering thistles and particularly welcome after a few years when their numbers were thought to be declining. A few peacocks, commas and small skippers added to the mix. I searched the few hedgerow oaks for the purple hairstreaks I had recorded in the previous two years but could find none.

The briefness of butterfly lives was emphasised by my second visit to the area a month later when I saw only one small tortoiseshell and no ringlets or meadow browns at all.

Early August found us in a very different habitat, a thousand feet up in the grassland above Bastow Wood in Upper Wharfedale, just outside Grassington. Here the grass was dotted with harebells, scabious, the yellow plumes of lady’s bedstraw, purple flowering betony and, along the lines of limestone outcrops, yellow rock-roses. Feeding on spear thistles and betony (pictured) were the butterflies for which we were searching, dark green fritillaries, distinguished from Britain’s other two large fritillaries by the distinctive pattern on the hind underwing.

Around the same spot were lots of small heaths and a few common blues while meadow browns, ringlets and a few small tortoiseshells provided an overlap with the butterflies of Lower Wharfedale. We searched in vain for the other two specialities of Upper Wharfedale, the northern brown argus which lays its eggs on common rock-rose and the Scotch argus which does the same on blue moor-grass. Finding those remains a challenge for next year.

Denis O’Connor