Satyrium w-album
This butterfly was thought by many to be a certainty for extinction
following the ravages of Dutch Elm Disease over succesive decades since
1970 on one of its main larval foodplants, English Elm.
There is evidence that the species is doing surprisingly well. It is
thought to be seriously under recorded across its range, partly due
to its secretive lifestyle atop the elms in the earlier phase of its
adult life. There is evidence that once mating has been completed the
butterfly becomes more accessible, coming down to nectar plants such
as thistle.
In 2006 I made a concerted effort to build on my poor knowledge of the
range of this butterfly in my area of Buckinghamshire. I believe that
I looked for this species too late in former years . A good friend with
much experience of this species in South London and Surrey corrected
me in stating that Satyrium w-album in fact has an overlap with the
Black Hairstreak adult flight period and is on the elms in June.
This was key to my approach this year as well as building an awareness
of the presence of healthy elms well in advance of the emergence of
the butterfly in June. This monitoring of healthy elm will be an ongoing
effort over the coming years as elm can quickly succomb to DED.
I was very pleased to locate several new colonies this year, eight in
all. Unfortunately my field trips are restricted at this time of year
to the homeward car journey from work. However the familiar journey
allowed me to build a picture of available healthy elms over preceding
months, albeit from the car. I find that once likely elm is located
more suitable specimens are often apparent on roadsides and adjacent
fields.
July 1st was peak day for me this year with 34 individuals between 3
sites close to Aylesbury. However the following day was my most rewarding
with a single adult White Letter Hairstreak on a 'juvenile' elm near
Wendover, a success at last on a tree I had checked out over the previous
three years. It was sad to note that by August there were signs of DED
on that very tree.
I believe that the White Letter Hairstreak is a butterfly that is often
overlooked. I hope to build on my small successes this year over the
coming seasons.
Tom Dunbar