It is thought by some that this species was an unofficial re-introduction in the early 1990s but there is no evidence to support that theory, perhaps just a reluctance to accept it had not been recorded for many years. Under-recording is common with several species in Cumbria. The species was recorded in Cumbria and put on the 1947 and 1971 distribution maps but was not re-discovered again until 1991 in Witherslack Woods deep in an area away from public paths or rights of way. In the absence of other evidence we should accept that it did in fact survive in very low numbers away from the gaze of experts in a remote part of somewhat dense woodland. In the years following its discovery the woodland owners coincidentally carried out a huge thinning out of the woodland and that was exactly the trigger for the Silver-washed to thrive and thrive it did along with a big rise also in High Brown and Pearl-bordered populations there. The Silverwashed has expanded its range to other nearby woodlands and to Roudsea Woods some miles away. However, the Witherslack Woods colony again declined due to lack of woodland management and is now at a low level although current management work by this Branch and other environment schemes is attempting to halt and reverse that decline.
Where to look
Anywhere in the wooded areas of Whitbarrow Scar where the public have access. A small population is present in Brigsteer Woods, SD487883 and it flies in reasonable numbers in the Roudsea Woods NNR SD330826 but a permit is required from Natural England (telephone 015395 31604) to access the latter woodlands.
When to look
In Cumbria it is slightly later than the south of England colonies. Try about the second week of July through to the end of August.