A butterfly special to the Isle of Wight

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Sudmoor on the seaward edge of the Mottistone Estate is a great place to spot butterflies, especially the rare Glanville fritillary. By far the largest population in the UK is found on the cliffs here on the south coast of the Isle of Wight.

The Glanville fritillary is one of the smaller fritillaries. It's very active with rapid wing beats and a short glide.

They rarely settle, but when they do, maybe to bask in the sun, you can see their beautiful orange and brown chequered patterning, and cream and orange bands on the underside of the wing.

An ‘insane’ 17th-century lepidopterist?

The Glanville fritillary was named after Lady Eleanor Glanville, a 17th-century butterfly enthusiast with no links to the island. She actually discovered it in Lincolnshire, far to the north of its normal range.

Lady Eleanor’s family thought she was mad to have such an odd hobby, and even went so far as to challenge her will on the grounds of insanity.

Life cycle of the Glanville fritillary

The Glanville fritillary butterfly lays its eggs on ribwort plantain in a warm, sheltered site. The caterpillars have a distinctive black body and red head, and emerge in February or March. They feed almost exclusively on ribwort plantain with a voracious appetite. They prefer the young plants that tend to be found where the cliff is crumbling away and there is little competition from other vegetation.

The butterflies emerge from the pupae in late May and June, but have a lifespan of only a few weeks. They feed on nectar from cliff-top flowers such as wild carrot, thrift and bird’s foot trefoil.

Population fluctuations

Glanville fritillary population numbers fluctuate wildly from year to year. In good times there may be thousands of caterpillars, but a spell of bad weather or an attack by parasites will cause the population to suddenly crash, leaving few survivors.

However, when this happens the parasite also disappears. But the butterfly somehow manages to cling on and its numbers can recover amazingly quickly. In a few years there will once again be thousands of caterpillars.

2010 and 2011 were good years with the butterflies spreading out from the coast to be seen far and wide over the island.