Dusky Large Blue (Phengaris nausithous)
2024 photographs highlighted in yellow. Click on any photograph to go to an enlarged picture, or simply scroll down the page.
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| 31074_male_Jura_11Jul12 | 30944_male_Jura_11Jul12 | 30986_male_Jura_11Jul12 | 31048_male_Jura_11Jul12 |
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| 44924_male_Isère_27Jul17 | 44931_male_Isère_27Jul17 | 44934_male_Isère_27Jul17 | 44952_male_Isère_27Jul17 |
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| 50029_male_Isère_18Jul22 | 50118_male_Isère_23Jul22 | 50187_male_Isère_23Jul22 | 44983_pair_Isère_27Jul17 |
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| 50159_female_Isère_23Jul22 | 30973_female_Jura_11Jul12 | 31004_female_Jura_11Jul12 |
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A Phengaris species of the wetlands of central
Europe, with the distribution just spilling into eastern France. It is very
strongly tied to the larval hostplant Great Burnet (Sanguisorba officinalis)
as can be seen from these photographs. Because of its habitat requirements, it is
quite rare and highly localised in France and in serious danger because of the drainage of the
wetlands. It is highly sedentary and can often occur in just one small area of a
suitable habitat, often in the drier margins of the wetland. It usually occurs
at medium altitudes of around 1000m. It is a very well-named blue, as it is decidedly dusky in appearance, even the males for whom the upperside black borders are quite broad and the blue scales quite subdued. The female has no blue scales. Both sexes tend to spend all of their time on Sanguisorba flower heads, even when roosting, and rarely - given my limited experience of this species - show open wings. The undersides of both sexes are rather similar, but can be fairly easily be told apart in flight when the blue of the male is apparent. |
Like other Phengaris species, nausithous has a close relationship with Myrmica ants, particularly M. rubra. The eggs are laid on the Burnet flowers (see 31004 and 50159) and the larvae, after the third moult, are taken into the ants nest where they are fed on ant larvae.
The butterflies are single-brooded, emerging at the end of June and flying until August, although the males I saw on 11 July 2012 looked distinctly worn. However, it appears that the flight periods of colonies, even those not too far apart, can vary substantially, and at the site in Isère I visited in 2017 at the end of July they were still very fresh. This particular site was exceptional for both nausithous and the Scarce Large Blue (P. teleius), with around thirty of each species flying in a limited area of Sanguisorba. It was a surprise to me that even a small amount of Sanguisorba can support even a medium-sized colony.
This species was previously known as Maculinea nausithous. |
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ref |
sex |
observations |
alt. m |
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31074 |
M |
a couple in courtship, the male below, just showing the blue of the upperside. |
1060 |
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30944 |
M |
a male, showing the cinnamon colouring of the underside. |
1060 |
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30986 |
M |
a male, with rather well-developed underside markings. |
1060 |
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31048 |
M |
a male, showing signs of wear. |
1060 |
| 44924 | M | a male, with quite a rich cinnamon colour. | 340 |
| 44931 | M | a male, with a very deep cinnamon colour. | 340 |
| 44934 | M | a male, nectaring (or about to) on the Sanguisorba judging from the proboscis. | 340 |
| 44952 | M | a male, quite pale in comparison to the others at this site. | 340 |
| 50029 | M | a fresh male, with the cinnamon flush very much in evidence. | 340 |
| 50118 | M | a fresh male, with the cinnamon flush very much in evidence. | 340 |
| 50187 | M | a fresh male, with rather bold black spots and bright yellowish surrounds which accentuate the black spots. | 340 |
| 44983 | PAIR | a mating pair. Even the mating tales place on a head of Sanguisorba. | 340 |
| 50159 | F | a very fresh female, with the cinnamon flush, its body arched in the act of agg-laying. | 340 |
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30973 |
F |
a female. |
1060 |
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31004 |
F |
a female, egg-laying. |
1060 |
