Posted by Tony Irwin on 11-05-2026 18:12
#4
The back lighting does make the fly look rather brown, but it is grey enough to be
lacustris. The shape of the wingspot is large and oval in
stagnalis, unlikely to form a dumbell shape when the wings are overlapped.
The listing of
lacustris as a synonym of
stagnalis is wrong. If you read the abstract of the quoted paper (Zatwarnicki and Irwin 2018), it clearly states that
tenuicosta is a synonym of
lacustris. I don't know why the confusion has arisen, but thanks for pointing it out.