One day in August this year I took several photographs of a rather striking fly that was resting on one of the leaves of the dwarf elm (Ulmus glabra ‘Nana’) in the middle of the Rock Garden. I was unable to identify it at the time, but while browsing the internet in a so far unsuccessful attempt to identify another fly-like insect I had found yesterday, I came across photos that matched the ones I had taken back in August. It turns out that I had photographed Peplomyza litura, a member of the fly family Lauxaniidae. There were no published records of this fly from Scotland until 18 years ago, when Rotheray (1998) published records of adults and larvae he and others had found in various parts of Scotland, including Edinburgh, between 1993 and 1996 as well as old museum specimen records from Scotland, some dating back as far as the first decade of the 20th century. From these he considered that Peplomyza litura was widespread in Scotland, at least between the central belt and Morayshire.
There are still relatively few Scottish records of Peplomyza litura, and it is obviously under-recorded in Scotland. Recent photographs from the Edinburgh area found on the internet include one from the city in 2011 and another from Cramond in 2013. My August 2016 sighting at RBGE is of course a new Garden record.
As can be seen from the accompanying photographs, Peplomyza litura is quite easily identified by the rather smoky-brown wings that are almost black in their rear half. The thorax is also streaked and the eyes are a rather vivid red. All the legs are entirely pale-coloured – there is one other British species of Peplomyza, P. discoidea, which looks very similar to P. litura except that all the legs are partly dark-coloured.
According to Rotheray (1998), Peplomyza litura has a long flight period in Scotland, from mid-June to late September. The larvae typically feed on decaying wood and Rotheray’s adult records were from fallen logs whereas the one I saw was resting on a leaf. Rotheray commented there were also larval records from a rook’s nest and from a leaf mine in a decayed leaf of crab apple.
Keep a look out for this rather distinctive fly next summer.
Reference: Rotheray, G. E. (1998). Peplomyza litura new to Scotland and description of the third stage larva (Diptera, Lauxaniidae). Dipterists Digest ser. 2, 5: 12-15.