Phengaris nausithous

Dusky Large Blue


by Matt Rowlings

copyright © 2003-2024

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Vaud, Switzerland, June 2012

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Vaud, Switzerland, June 2012

Field notes and information

This species is so dusky, it looks rather like one of the heaths, Coenonympha. The very dark blue of the male upperside is quickly apparent after brief observation however.

Identification & Similar species: No other species are similar, even amongst the other large blues, Maculinea. Lacks any submarginal markings on the underside hindwing.

Distribution & Flight: One or two small areas of northwest Spain with the main distribution from central eastern France, Switzerland, Germany (absent from the north) and eastwards.

Flight time seems to vary with locality and altitude. In Switzerland it flies early/mid July at 1400, but in August at 600m. In north Spain I have found it in very good condition in mid August at about 900m and 8 years later at the same site in mid July in good condition.

Habitat & Behaviour: Marshland, which may be fairly dry in the summer where the larval food plant great burnet, Sanguisorba officinalis, grows. Adults will often sit head down on the flower heads of Sanguisorba where they are surprisingly inconspicuous. In this position they often curve their abdonmen around the flower head. In the heat of the summer in Spain they will rest like this for a considerable amount of time unless disturbed when, in the afternoon of a very hot day, they will walk round the flower head rather than fly.

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Vaud, Switzerland, June/ August 2010

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Fribourg, Switzerland, June 2021

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Vaud, Switzerland, June 2012

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Vaud, Switzerland, June 2009

Egg laying and eggs in the head of the food plant Sanguisorb.

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Soria, Spain, July 2011

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Vaud, Switzerland, June 2022

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Vaud, Switzerland, June 2022

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Vaud, Switzerland, June 2012

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Fribourg, Swizterland, June 2015

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Vaud, Switzerland, June 2007

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Vaud, Switzerland, July 2013

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Vaud, Switzerland, June 2012

Egg laying.

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Vaud, Switzerland, June 2012

A male telejus is trying to mate with a female nausithous. She's not interested at all.