Sussex Butterfly Conservation : Species

Butterfly Species in Sussex

Female Adonis Blue with open wings - photo by Dave Brown

Adonis Blue

Polyommatus bellargus

Description

This species is a downland specialist, with Horseshoe Vetch its sole larval foodplant. Two of my favourite mantras are: “Find the larval foodplant, find the butterfly” and “Understand the foodplant, and begin to understand the butterfly”. On the South Downs, Horseshoe Vetch is a common plant that is found in species-rich chalk turf, and mostly on south-facing slopes. It is easily swamped by more vigorous plants and requires a short sward to flourish (that means grazing animals, preferably rabbits). This vetch is common on the eastern downs but becomes increasingly scarce, west of the River Adur. Moving further west, it is difficult to find Horseshoe Vetch west of the River Arun as the remaining small remnants of good-quality chalk turf are generally north-facing.

In the 1990-1994 county survey, a few Adonis Blue colonies were found west of the Arun, but in the 2010-2014 survey, they had all disappeared.

The brilliance of the blue together with the chequered white fringe of the outer wings readily identifies the male. An older male that is a much paler blue and has borders that have worn away, can look like a male Common Blue, but even when the specimen is very worn there are usually one or two smudges on what remains of the border to help with the ID. A female Adonis Blue can be easily confused with a female Chalk Hill Blue, but this is only a problem when the two species overlap in late summer.

Between 2006-2024 an “average first sighting” was May 7th (range, April 24th to May 23rd). With such a wide range of dates, it is apparent that the emergence of this species is heavily influenced by the spring weather. There is a second emergence in late summer, often when Chalk Hill Blue is in steep decline, and this helps to differentiate between the females of these two species.

For the years 2006-2024 the “average last sighting” was September 28th (range, September 4th to November 16th).

Where to find

Locations to see Adonis Blue, include: Anchor Bottom at TQ205093, Beachy Head at TV562957, Castle Hill at TQ368068, Mill Hill at TQ210073, and Medley Bottom (Amberley) at TQ044116.