Pearl bordered fritillary

Sexes are similar in size, but females are slightly bigger. Males are often seen flitting and gliding low over the ground in search of females. In spring the black caterpillars with pairs of yellow hairy spikes on each segment are seen basking on dead bracken. Adult butterflies are often seen congregating in sheltered sunny sites, where there are nectar plants.

Look for the caterpillars emerging from hibernation in March. They pupate and turn to a chrysalis on the ground between April and early June and adult butterflies are seen from late April until the end of June. Eggs are laid near to food plants and incubate in a fortnight between June and July. The caterpillars emerge and feed on common dog violets until they hibernate beneath bracken litter in early September.

In Scotland the most recent surveys have identified 150 colonies on 120 sites. The right sort of habitat for these butterflies is often created by the way leaves cut under power lines. It is thought that there are more sites throughout Scotland that are still not reported. They live in specific colonies preferring dry and sunny, south-facing sheltered sites with short vegetation. They need these warm micro-climates for the caterpillars to get an early start in the spring. Adults often congregate in sunny sheltered sites on nectar plants.

Do not confuse with the more common small pearl-bordered fritillary whose butterflies are active between June to mid July. Both butterflies are best identified when their wings are folded up at rest. The pearl-bordered fritillary has a small black dot, only two inner white cells and the chevrons near the edge of the wing are brown.