Phengaris alcon

Alcon Blue


by Matt Rowlings

copyright © 2003-2024

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Photo: alcon4.jpg

SE Serbia, June 2012

A roosting butterfly, found at dusk.

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SE Serbia, June 2012

Field notes and information

One of the large blues, Maculinea , it is separated from them by a violet blue upperside, and lack of black spots (except in some particularly dark females). The adults seems to be rather harder to find than the eggs, which are very conspicuous on the flowers of the larval food plant.

Identification & Similar species: The mountain alcon blue, rebeli, is now generally recognised as a form of the current species that exploiting a different habitat where an alternative food plant which is used.

Other large blues have black spots on the upperside of the male. It has a single row of post discal spots on the underside.

Distribution & Flight: North Portugal, west Pyrenees, much of France and eastwards across Germany and to north Greece. Flies during a brief period from mid June (eg Serbia) to mid August (eg west Switzerland).

Habitat & Behaviour: Damp meadows below 1000m. Larvae feed on marsh gentian, Gentiana pneumonanthe.

Variation: The form rebeli was briefly considered to be a separate species. It can be separated with difficulty by the narrower black margins of the upperside male and limited blue basal areas in the females. The food plants are different too, with this form using cross-leaved gentian, Gentiana cruciata. Generally it flies at higher altitudes.

Photo: alcon2.jpg

Vaud, Switzerland, August 2006

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Vaud, Switzerland, August 2006

Photo: alcon1.jpg

Vaud, Switzerland, August 2006