Early Season Anthomyiid Flies

I spent most of Sunday the 5th of March trying to identify some Anthomyiid flies I had caught the day before.  There were 4 clean-looking light grey females with yellow halteres and 10 rather grubby little males.  I was using some draft keys produced by Michael Ackland.  I chose first to run the females through his partial key to species females.  The first 3 all ran through to different species in spite of all looking very similar.  None of these species had I come across before and I couldn't get any confirmation from photos on Diptera.info so I had very little confidence in them as identifications.  I eventually gave up and turned to the males. 

I picked out a male with a largish head and with Ackland's draft key to males it ran straight through to Egle ciliata.  A quick check on Diptera.info revealed several very similar images so I took this as a good identification.  The second male ran through to Lasiomma seminitidum which I had also never heard of.  The 3rd, 4th and 5th did the same and from the look of the remaining males it seemed likely that they would also go to the same species.  With so many males of the same species there must surely been some females around?  I went back and ran the first female through the draft female key backwards from Lasiomma seminitidum and it matched every couplet.  The other females did the same.

So what I had was 4 females and 9 males of Lasiomma seminitidulum along with the 1 male of Egle ciliata.  But how come I had not even heard of such an obviously common fly before?  More or less as a last resort I decided to look up Lasiomma in the Genera Characteristics section of Ackland's draft key.  There it stated: "L. seminitidum being one of the earliest species to emerge in early March".  Then I realised I hadn't wasted my day.