Individual on avalanche drift at 1800m, Switzerland, May 2018
The context of the picture above. The butterfly was perfectly happy,
choosing
preferentially to land on the snow.
Another individual above the May snowline in Switzerland, showing much
weaker markings.
Strength of markings is very variable and apparently not related to
altitude, climate &c.
Female laying on birds-foot trefoil, Switzerland, May 2015
Egg on birds-foot trefoil, Switzerland, May 2015
Egg, Switzerland, June 2011
Male, Italy, April 2013
Male, Switzerland, April
2010
Switzerland, April 2008
Switzerland,October
2010
(yes, October ...!)
Distribution
In much of Europe, this is
the commonest
hairstreak, flying from March at low altitudes in the South through to
July at higher altitudes and in the North. Males are pugnacious little
creatures, vigorously defending their favoured branch of a bush or tree
and darting out to challenge any passing insect. Females are more
commonly seen as they go about the more lesiurely - but vitally
important - business of laying eggs. Both sexes have a slightly
tumbling flight, when they appear as generally dull, small butterflies
but with occasional flashes of that brilliant green underside.
As these pictures show, there is great variation in the extent
and
solidity of the 'hairstreak' on the underside of this butterfly.
Sometimes it is effectively absent, sometimes just a dash or two on the
hindwing, sometimes
it covers the width of the hindwing but not the forewing and sometimes
it is prominent on both wings. Nevertheless, in most of its range this
species is unmistakeable, being the only butterfly to have green
undersides (which it invariably shows on resting, the uppersides
never being visible). Only in parts of the Mediterranean region, where
the very similar Chapman's green hairstreak flies, is
confusion ever likely to arise. This latter butterfly is local and
uncommon and I have yet to see one on my occasional spring forays to
Spain. It is best
separated from the green hairstreak by the eyes, which have a buff or
rusty lining around them rather than the striking white-rimmed
spectacles of the green hairstreak. Many of the pictures on Matt Rowlings's web page show this
well.
Despite the name, this species is not particularly associated
with
bramble (Rubus)
but will take a very great variety of different hostplants - including
bramble. Pea species are often used, from small herbs like birds-foot
trefoil to woody species like gorse and broom. The only real habitat
requirement seems to be an availability of suitable bushes for the
males to perch on and defend. There is a single generation each year.
This means pupae formed in May or June must remain in this state until
the following spring. Very occasionally, a few emerge out of season. I
have seen one individual - the last picture above - in October, in a
year when early snows followed by a thaw might have created a false
impression of winter. I'd like to think it wasn't the only one that
year and that it could have enjoyed some kind of social life, but as a
rule there is no second generation even in exceptional years.
