Large Blue (Phengaris arion)

Male. Taken at Daneway Banks, Glos., on June 16th 2014.
(1/160th sec at f13. Approx 2.5x lifesize. © David Hastings)

Male underside. Taken at Collard Hill, Somerset, on June 15th 2015.
(1/800th sec at f14. Approx 2.5x lifesize. © David Hastings)

Female underside. Taken at Daneway Banks, Glos, on July 8th 2013.
(1/160th sec at f13. Approx 2.5x lifesize. © David Hastings)

Mating pair. Taken at Daneway Banks, Glos, on June 25th 2016.
(1/500th sec at f13. Approx 2x lifesize. © David Hastings)


Wing span: 41 - 50 mm

The British subspecies of this butterfly became extinct in 1979. A similar Swedish subspecies was introduced to a few sites in south-west England in the 1980s.

This species is restricted to a few sites in the Cotswolds and Polden Hills.

It requires warm, well-drained grassland, often on limestone. These conditions are needed by the red ant Myrmica sabuleti as well as the Large Blue itself.

The female Large Blue will only lay eggs on Wild Thyme (Thymus polytrichus). Young larvae are cannabalistic, and only one larva will survive per plant. Upon reaching its fourth instar the larva drops to the ground in the hope of being found by a red ant. The ant causes the larva to secrete a droplet from a special gland located on its 7th segment. Eventually, after a period from 30 minutes to 4 hours, the larva distorts its body by rearing up on its prolegs, to give the illusion of being an ant grub. This causes the ant to pick the larva up in its jaws, and carry it back to its nest. Once within the nest, the larva feeds on the ant grubs, which it may do for two years. The larva pupates in the nest, where it continues to be cared for by the ants until it emerges and makes its way to the surface. Adults only live for about five days, and are usually on the wing from mid-June to mid-July.

Wild Thyme (Thymus polytrichus) is the only larval foodplant prior to the caterpillars being taken into ant nests.

Adults feed primarily on Honeydew and Sap. Bugle, Carline Thistle and Thyme are also used.

Males patrol over grassland at the base of slopes, searching for females. They sometimes roost in the shade around mid-day if the weather is hot.

This species has Critically Endangered status on the UK list.


20-Jun-2019 : Daneway Banks, Gloucs (2)

25-Jul-2018 : Vercors Natural Park, France
21-Jul-2018 : Vercors Natural Park, France
20-Jul-2018 : Vercors Natural Park, France
21-Jun-2018 : Daneway Banks, Gloucs (10)
25-Jun-2016 : Daneway Banks, Gloucs (10m,1f)
26-Jul-2015 : Bansko meadows, Bulgaria
15-Jun-2015 : Collard Hill, Somerset (5)