Sussex Butterfly Conservation : Species

Butterfly Species in Sussex

Common Blue nectaring on Birdsfoot Trefoil – photo by Martin Kalaher

Common Blue

Polyommatus icarus

Description

This species can be found more-or-less anywhere in Sussex, wherever there is a warm patch of unfertilised grassland. It lives in discrete colonies of tens or hundreds of individuals and on the best downland sites it may very occasionally approach the one thousand mark, as at Chantry Hill on 16/08/2016, when there was an estimated 800-1000 individuals.

The uppersides of the male is a uniform lilac-blue, and the borders are pure white with no markings (no chequered border, as in Adonis Blue). Whilst the male is an easy ID, the female can be very confusing, as some are “mostly brown” (and can be confused with Brown Argus), some are “mostly blue” (and look like male Common Blues), and some are an eclectic mixture of all sorts of colours.

Between 2006-2024 the “average first sighting” was May 5th (range, April 21st to May 12th). This first brood peaks in late May or early June and flies to early July. The second brood flies from mid-July to early September, with a peak during the first week in August. In most years there is a very small third brood from mid-September to late October. In the years 2006-2024 the “average last sighting” was October 27th (range, October 5th to November 15th). The total flight period for their season is around six months.

The main larval foodplant is Birdsfoot Trefoil, which is ubiquitous in Sussex. Other plants used are Greater Birdsfoot Trefoil, Lesser Trefoil, Horseshoe Vetch, Black Medick and Restharrow.