Butterflies and Plants

Speaker: Nyree Fearnley 

Wednesday 13th March 2024 

Nyree’s enthusiasm for butterflies was utterly infectious as she described some of her favourite encounters with butterflies and her endeavours to seek out some of Britain’s less common species. The talk was illustrated with superb photographs Nyree had taken herself, which included interesting images of caterpillars and eggs as well as the adult butterflies. Nyree’s love of both botany and butterflies is well matched - Nyree began by saying that if a site is good for botany, it’s usually good for butterflies too. In trying to tailor this talk for botanists, Nyree included many references to caterpillar food plants. Here are some of the things we learnt.

If you see a blue butterfly in a town, it’s likely to be a Holly Blue. This species has two generations of butterflies each year which feed on separate food plants. Eggs are laid on Holly in spring but on Ivy in autumn. Why they do this is a mystery. Nyree showed photos of Britain’s more common butterfly species in the approximate order they are first seen each year as adults. Early appearing species are those that overwinter as adults such as Brimstone butterflies. Although adult Brimstones are easy to identify, the caterpillars are extremely well camouflaged as Nyree demonstrated on a photograph. Goodness knows how she spotted it!

Red Admirals are classed as a migrant, but some are now resident, due to our changing climate. Adult Ringlets and Meadow Browns are often in flight together in grassland habitats. The wings of Ringlets have many false-eye markings and if you look carefully, the edge of the wing has a narrow white border.

Purple Hairstreak butterflies, which appear to have been extending their range northwards, spend most of their time in the canopy of oak trees. Using binoculars, Nyree has often seen them sitting on leaves high up in the canopy. The adults feed almost entirely on honeydew deposited by aphids rather than visiting flowers for nectar. Only occasionally will they come down to the ground to feed on minerals.

Nyree described Green Hairstreaks as ‘exquisite little butterflies’ with their distinctive iridescent green underwings which change colour depending on the angle of the sun. Although the species is declining overall in Britain, as one of the caterpillar food plants is bilberry, there is no shortage of habitat for them here in Yorkshire. Green Hairstreaks establish territories and fiercely drive off not only rivals, but anything that flies past.

In the Yorkshire Dales, Northern Brown Argus are at the southern end of their range in Britain. If present, the eggs are easily spotted on the leaves of Common Rock-rose. Look for the eggs in July and August on the upper side of the leaf, bang in the middle, on the central vein. The caterpillars feed on the underside of the leaves, leaving the upper surface intact. Nyree explained how to distinguish between adult Northern Brown Argus and Common Blue butterflies, and has some info sheets she could bring along to a field meeting.

The Scotch Argus is very common in Scotland but we do have five known colonies in West Yorkshire, including at Bastow Wood near Grassington. On a sunny day in August you are almost guaranteed to see it there. The wings have distinct orange bands containing black spots with white centres. The caterpillar food plants are Purple Moor-grass and Blue Moor-grass.

Nyree was delighted to see her first Chalk Hill Blue butterfly last year on the Isle of Wight. Nyree has visited the Isle of Wight before, but this time her visit was timed perfectly for this species. She saw lots of males flying about, but only two or three females which she found head down on grass stems, waiting for males to find them. The caterpillars feed solely on Horseshoe Vetch, with the species restricted to southern England.

Nyree’s talk was packed full of interesting information and entertaining stories. Such was the disappointment of some members to have missed the talk, Nyree agreed to do a re-run via Zoom on 4th April. Nyree called for volunteers to step forward to help with butterfly surveys this year at the Denton Estate near Ilkley. Please contact Nyree if you are interested in volunteering.

Text by Susan Simcock

Photos by Nyree Fearnley