Eristalinus sp.

peterbolson · #1 (**permalink**) 17-08-2010, 01:58 PM

I can't make up my mind whether this is aeneus or sepulchralis.
Found on ragwort at Wedholme Flow peat moss NNR, about 4 miles from the mudflats of the Solway. WL 8-9mm. The thoracic stripes suggest sepulchralis, but the lower parts of the eyes are definately non hairy ( microscope ) which points to aeneus.
I've not seen either before so an ID would be very welcome.
Peter

Geoff F · #2 (**permalink**) 17-08-2010, 08:28 PM

I suspect this is a suitable subject for Roger Morris.

Stubbs does state that the sepulchralis lower eye hair can be very weak. And aeneus has a black thorax 'on the specimens examined' so there may be room for some doubt there.

But I can't really offer any more suggestions than what you already have here.

Jason Green · #3 (**permalink**) 17-08-2010, 08:33 PM

Evening Peter,

Agree with Geoff's reasoning - likely Eristalinus sepulchralis. I had my female out under the 'scope, and it does take some searching. The hair was particularly sparse on the lower-eye, but being potted in London I won't entertain the idea of aeneus.

Try examining the eye side-ways, viewing from the back and to the eye's left against a white specimen plate.

Otherwise, everything matches my sep.!

Take care,

Jason

Matt Smith · #4 (**permalink**) 17-08-2010, 08:48 PM

I'd go for E.sepulchralis. I don't see E.aeneus very often, it seems to be a real "seaside" species while E.sepulchralis pops up in most places. In "jiz" terms, I find E.sepulchralis to be "black and dumpy" while E.aeneus is "bigger and obviously shiny bronze-black".

Matt

peterbolson · #5 (**permalink**) 17-08-2010, 09:56 PM

Thanks guys.
I think Matt is right about the jizz. It's an odd looking hoverfly, dull and dumpy with rear legs that seem too long so it seems to walk tipped forwards. Hardly the "magnificent hoverfly" of S&F ! I think it must be E.sepulchralis so I'll have another look for those eye hairs, which should cover the entire surface.
Incidentally Stubbs says that the hairs on the lower part of the face ( not the eyes ) can be weak in E.sepulchralis but can extend more than halfway down .
Peter

peterbolson · #6 (**permalink**) 18-08-2010, 07:51 AM

Well, I have had a really good look and although I can't say it's completely bare the lower third is virtually bare - very very few hairs, possibly a dozen or so in each eye. I suppose it depends how you define bare. I think alot of bare eyes do in fact have the occasional hair on them. You certainly wouldn't see these without a microscope.
Peter