Sussex Butterfly Conservation : Species

Butterfly Species in Sussex

Small Tortoiseshell nectaring on a purple Hebe – photo by Martin Kalaher

Small Tortoiseshell

Aglais urticae

Description

A few hibernating adults emerge in January or February (2006-2024 average “first sighting date” was February 7th), but significant numbers are not recorded until there are a succession of warm, sunny days in March. Emerging adults quickly mate, and the females lay their eggs on Common Nettles. The first brood begins its emergence in late May and peaks in late June. There is a significant overlap between the first and second brood, which begins its emergence in mid-July, with a peak in late July and early August. Small Tortoiseshells enter hibernation quite early and in the years 2006-2024 the “average last sighting” was October 25th (range September 18th to December 29th).

In the early 21st century this species was widespread and common throughout the county. In late summer it wasn’t unusual for a single Buddleia bush to be covered in a dozen or more Small Tortoiseshells, but this doesn’t seem to happen, anymore. This sad and very serious decline in its fortunes is presumably multi-factorial. Parasitoid wasps and flies have played their part, as has the recent arrival of Sturmia bella, a tachinid fly that lays its eggs on the nettle leaves, adjacent to feeding caterpillars. Climate change may prove to be the biggest factor, for with warmer winters we have earlier springs, which in turn has brought forward the first breeding cycle by around three weeks, allowing for a regular second brood. Historically, the second brood was only occasional, but now it has become an annual event there could be very significant problems if it partially fails due to bad weather. Fewer adults in late summer leads to fewer adults hibernating in the winter, and this means that the population is likely to point towards a downward spiral. Time will tell, but the portents for southern England do not look good.

Where to find

Somewhat less predictable compared to yesteryear, but four sites are worth a visit, along the Cuckmere River between Litlington and Alfriston at TV520025, Ferring Rife (TQ091015 to TQ089024), Steep Down near Sompting (TQ162079 to TQ168079 and TQ166076), and in the autumn, Herstmonceux Castle at TV645105.