Sloe Hairstreak
Satyrium acaciae

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Satyrium acaciae

Switzerland, June 2017

Satyrium acaciae

Switzerland, June 2017

Satyrium acaciae

Switzerland, June 2017

Satyrium acaciae

Male, Switzerland, June 2018

Satyrium acaciae

Female, Switzerland, June 2018

Satyrium acaciae

Female laying an egg, Switzerland, June 2018

Satyrium acaciae egg

The egg she laid, clothed in hair-scales

Satyrium acaciae egg

Another view of the same egg

Satyrium acaciae

Switzerland, June 2017

Val d'Aran, July 2008

Val d'Aran, July 2005.

Val d'Aran, July 2005

Satyrium acaciae distribution

Distribution

The sloe hairstreak is widely distributed across Europe but generally rather local. I know of several sites in Switzerland where it is supposed to fly but have only actually seen it at one. There, it is in fact very common. The species likes grassy areas with copious sloe bushes and plenty of sun.

Identification is not a problem, given a good view. Most obviously, the orange lunules on the hindwing are confluent, forming something closer to a band than a series of spots. They may enclose a blue spot near the anal angle but this is neither as large nor as deep blue as in blue-spot hairstreak. The butterfly is also smaller than that species and the hairstreak is less bold. Like many other Satyrium species, sloe hairstreaks enjoy sitting on umbelliferous plants like yarrow, though they also enjoy the privet that grows among the sloe bushes.

The female sloe hairstreak has a brush of black hairs on her abdomen, some of which she carefully transfers to each egg she lays, rendering it much less visible than it would otherwise have been. This shaky video - I tried not to approach too close - shows one doing just this:

Many of these hairs wear off soon but while they last the egg is really quite inconspicuous. It is in this stage that the sloe hairstreak passes the winter, emerging as a caterpillar in the spring, to feed up for a June-July flight period. I have seen relatively fresh adults at the end of July in the Pyrenees at about 1600m.