60. Polyommatus damon (Denis & Schiffermüller, 1775) / Damon blue / Lycaenidae – Polyommatinae
NL: witstreepblauwtje / D: Grünblauer Bläuling / F: le sablé du sainfoin
Photographs: Sepp Weidemann, Frits Bink, Frits Bink ©.
Small, wing length 15 (14-16) mm. Extinct. The presence of the species in the Benelux may have been as a result of the traditional agricultural practise of growing sainfoin as a crop. The last specimens were collected in 1944 from a locality near Antwerpen (Maes, Vanreusel & van Dyck 2013: 377).
The butterfly is on the wing from early-July until end-August in central Europe, in the southern part until mid-September. It peaks end-July. Required heat sum is 750°d and the maximum tolerated 2000°d, corresponding climate windows are24 and 38 weeks. It is known from sub-continental to continental climates, amplitude 8 to 17.
The clover sainfoin was introduced in the sixteenth century in the northern parts of Europe as fodder plant for cattle and for soil improvement and became widespread in grassland on chalk soils. It is not before this agricultural improvement that this oligophagous species could establish itself in central Europe (Ebert et al. 1991 (2): 366-371).
Behaviour over time
Overwintering: egg or fresh hatched larva in the fissure of the seed or in the empty calyx.
Reproduction: oviposition starts after 8-10 days when the body contains 103 (95-110) eggs, potential production 1.1 times more.
Larval feeding periods: 70 (58-92) days in the period end-March until end-June.
Spreading of risk: spread in appearance of the adult butterflies.
Life cycle: egg, 4-39 weeks; larva 8-43 weeks; pupa 28 (26-30) 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 perches.
Orientation in the landscape: short to tall grassland, also arable fields with sainfoin.
Oviposition: on the seeds or in the wilted calyx of the host.
Threats from other organisms: does not have any defence.
Myrmecophily: not often tended by ants but full array of ant-attracting and appeasing organs present.
Threats from the environment: butterflies tolerant of drought and heat.
Adult: nectar of flowers of herbs.
Larva: first instar feeds on the young shoot, then on the flower buds as soon as these are available and later on the mature leaves where it scratches the epidermis.
Plant species: Fabaceae, Onobrychis viciifolia.
Rearing experiment based on specimens from St Savernin-sur-Apt, France:
22 September 1987: eggs collected from arable field with cultivated Onobrychis viciifolia.
13 February 1988: one first instar larva started to feed on a young leaf.
28 February: in moult L1-2.
26 March: larva in third instar, fed on young leaf.
31 March: fed on the same shoot, scratched the leaf.
16 April: larva moulted to fourth instar, in appearance looked similar to fully grown larva.
19 April: larva fed on the very young flower bud, the whole inflorescence was only 15 mm long.
30 April: larva moulted.
15 May: larva pupated.
10 June: adult appeared.
Table 60-1. Results of dissections
Table 60-2. Collection and observation localities
D, Pottenstein, 475 m, 49° 47’ 25”N – 11° 25’ 16”E; 23 July 1984.
F, Apt 43° 54’N – 5° 24’E; 22 September 1987.
F, Aurel, 400 m, 44° 43’N – 5° 16’E; 29 August 1984, 2 September 1984.
F, Vallouise, 1200 m, 44° 51’ 18”N – 6° 29’ 28”E; 3 September 1982.
Fig. 60-1. Polyommatus damon, phenogram adapted from Ebert & Rennwald 1991b: 369.
Fig. 60-2. Polyommatus damon, habitat characteristics.
Fig. 60-3. Polyommatus damon, climate matrix, heat-sums 750 - 2000°d.