Logo Phegea Butterflies in the Benelux
Frits Bink & Rosita Moenen 2015

Based on: Dagvlinders in de Benelux 2013
Revised and extended
Edited by Sylvain Cuvelier & Peter Russell

Vlaamse Vereniging voor Entomologie
VVE Werkgroep Dagvlinders

Flemish Entomological Society
VVE Workgroup Butterflies

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64. Polyommatus dorylas (Denis & Schiffermüller, 1775) / Turquoise blue / Lycaenidae – Polyommatinae

NL: turkooisblauwtje / D: Steinkleebläuling, Wundklee-Bläuling / F: argus turquoise, l’azuré du mélot

Photographs: Frits Bink ©.

Small, wing length male 15 (14-16) mm, female 14 (13-14) mm. Disappeared from the Benelux, where up to 1957 it had occurred in a few places in the south of Luxemburg and Wallonia on scree with sparse vegetation.

The butterfly is on the wing from mid-June until late-July. It is known from sub-continental to mild continental climates, amplitude 8 to 13. Required heat sum 600°d and maximum tolerated 1800°d, corresponding climate windows 22 and 35 weeks.

The occurrence of this species in the Benelux was probably related to the human activities of mining and sheep breeding, because the steppe-like vegetation is not natural under the local climatic conditions.

Ecological characteristics

Behaviour over time
Overwintering: small larva in second instar in litter layer.
Reproduction: oviposition starts after 7-9 days when the body contains 40-60 eggs, estimated potential production 2.6 times as much.
Larval feeding periods: in summer 40 (35-46) days from end-July until end-September and in next spring 70 (60-79) days from end-April until mid-July.
Generations: one, in south Europe a partial a second.
Spreading of risk: not observed.
Life cycle: egg 10 (8-12) days, larva 46 weeks, pupa 22 (12-31) days.
Life span of adult: long, 4 weeks.

Photographs: Frits Bink ©.

Behaviour in space
From stay-at-home to migrant: stay-at-home, spatial requirement modest.
Finding a mate:
male patrols and perches.
Orientation in the landscape:
open and stony landscape with short vegetation and bare ground.
on thick leaves of small plants.

Threats from other organisms: the larva protected by ants.
Myrmecophily: strong, full array of ant-attracting and appeasing organs, at least in the fully grown stage almost permanently attended by ants.
Threats from the environment: endure heat and drought very well.

Feeding habits
Adult: nectar, all kind of flowers.
young larva in summer mines into thick leaves, in early summer when the larva has become bright green in colour, on shoot and flower bud.

Larval foodplants
Plant species: Fabaceae, Anthyllis vulneraria.

Rearing experiments based on specimens from Stenåsa, Öland, Sweden:
15 August 1983: female captured.
28 August: larvae already at end of first instar.
29 September: no larvae seen, all in diapause.
Overwintering outdoors.
13 March 84: pot taken indoors.
17 March: larvae ate upperside of the leaf or mined.
24 March: 2 larvae moulted L2-3.
10 April: larvae 6 mm in length, third instar?
20 April: 2 larvae in L4, yellowish in colour.
29 April: biggest larvae middle or end fourth instar, one in flower head.
2 May: some fed on flower heads, other continued to feed on thick and fleshy leaves.
4 May: 5 fully grown larvae, 4 feeding on flower heads, one still eating a leaf.
12 May: first larvae pupated.
15 May: prepupae observed, one in middle of final instar. 21 May: two pupae.
12 June: two adults appeared.
18 June: female hatched.
23 June: last pupa hatched, female.

Table 64-1. Results of dissections

Table 64-2. Collection and observation localities

F, Lorraine, Rupt devant Saint-Mihiel, 280 m, 48° 53’ 01”N – 5° 24’ 10”E; 28,June 2006.
S, Gotland, Buttle 57° 25’ 09”N – 18° 34’ 38”E; 19 July 1982, 16 July 2004.
S, Gotland, Lickershamn 57° 51’05”N – 18° 37’ 46”E; 17 July 2004.
S, Gotland, Maskmyr 56° 56 20”N – 18° 12’ 20”E; 25 June 2004.
S, Gotland, Russväter 57° 23 29”N – 18° 43’ 36”E; 16 July 2004.
S, Gotland, Stygmyr 57° 50’ 10”N – 18° 38’ 32”E; 18 July 2004.
S, Öland, Stenåsa 56° 32’ 44”N – 16° 36’ 43”E; 15 August 1983.
S, Öland, Eketorp borg 56° 17’ 43”N – 16° 29’ 10”E; 23 July 2004.

Fig. 64-1. Polyommatus dorylas, phenogram adapted from Ebert & Rennwald 1991b: 373.

Fig. 64-2. Polyommatus dorylas, habitat characteristics.

Fig. 64-3. Polyommatus dorylas, climate matrix, heat-sums 600 - 1800°d.

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Contact Werkgroep Dagvlinders: Jurgen Couckuyt