Dusky Large Blue (Phengaris nausithous)

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2018 photographs highlighted in green. Click on any photograph to go to an enlarged picture, or simply scroll down the page.

31074_male_Jura_11Jul12 30944_male_Jura_11Jul12 30986_male_Jura_11Jul12
31048_male_Jura_11Jul12 44924_male_Isère_27Jul17 44931_male_Isère_27Jul17
44934_male_Isère_27Jul17 44952_male_Isère_27Jul17 44983_pair_Isère_27Jul17
 
30973_female_Jura_11Jul12 31004_female_Jura_11Jul12  
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 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 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.

 

This species was previously known as Maculinea nausithous.

ref

sex

observations

alt. m

31074

M

a couple in courtship, the male below, just showing the blue of the upperside.

1060

30944

M

a male, showing the cinnamon colouring of the underside.

1060

30986

M

a male, with rather well-developed underside markings.

1060

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
44983 PAIR a mating pair. Even the mating tales place on a head of Sanguisorba. 340

30973

F

a female.

1060

31004

F

a female, egg-laying.

1060

 

31074_male_Jura_11Jul12

 

30944_male_Jura_11Jul12

 

30986_male_Jura_11Jul12

 

31048_male_Jura_11Jul12

 

44924_male_Isère_27Jul17

 

44931_male_Isère_27Jul17

 

44934_male_Isère_27Jul17

 

44952_male_Isère_27Jul17

 

44983_pair_Isère_27Jul17

 

30973_female_Jura_11Jul12

 

31004_female_Jura_11Jul12