Small black female hoverfly

peterbolson · #1 (**permalink**) 08-06-2010, 06:18 PM

Another one for Geoff

This is smaller than the others I have posted, WL 5-6mm. From woodland path.
There are some scanty short eye hairs & hairs on the humeri. I think it is probably one of the cheilosiini again.
Thanks
Peter

Geoff F · #2 (**permalink**) 08-06-2010, 07:19 PM

Well as a quick guess, I would suspect C. variabilis female.

Rather long darkish wings with dark orange stigma and black legs.

Short pale hairs on the frons which are inclined forwards but a few erect black hairs may be visible? And there should be some short spines underneath the hind femur.

Females are tricky though.

Can't you get some easy bright coloured species!

Having said that, I just struggled over a possible Syrphus ribesii with rather pale front and mid tarsi. I now think that must be the correct ID as I have (possibly) ruled out all the alternatives.

And I still have 2 days of general insect photos to sort through; but I suspect they are all rather mundane after already separating out a Chrysotoxum elegans.

oxycera · #3 (**permalink**) 08-06-2010, 07:38 PM

Try Chrysogasterini.

peterbolson · #4 (**permalink**) 08-06-2010, 08:11 PM

Sorry about the colour Geoff

. Nothing much flying at the moment in all this rain.
Isn't it rather small for variabilis ?
John, I did consider Chrystogasterini because of the shape of the face but couldn't make it fit any. Is the red colour on the sides of the abdomen just because she's pregant or is it part of it's normal colour ? It doesn't seem to extend round to the dorsum.
Peter

oxycera · #5 (**permalink**) 08-06-2010, 08:23 PM

Abdomen does look rather swollen but I don't think the red membranous area is unusual as such with this group.

Jason Green · #6 (**permalink**) 08-06-2010, 09:59 PM

Evening Peter,

Quote:

Originally Posted by oxycera

Abdomen does look rather swollen but I don't think the red membranous area is unusual as such with this group.

Yes, I'd say she's just gravid. I see the same/very similar on the female Platycheirus spp. I've seen - just stretched membrane.

Nice images.

Take care,

Jason

Geoff F · #7 (**permalink**) 09-06-2010, 02:18 PM

Without checking the book, I was thinking about C. variabilis females being a bit shorter than males.

But if we go smaller than that there are still a few Cheilosia possibilities to consider, and most of them are chiefly from your area.

So let's start with a few questions; would you describe the colour as solid black or a bit on the brassy side? Are the sternites well and equally dusted or plain/very slightly dusted? It is a bit difficult to tell from photos. Is the upper surface of the facial knob approximately horizontal?

Brassy coloured with fairly dense pale hair around the abdomen and well dusted sternites, face extensively dusted, frons with sides angled halfway along not straight - C. pubera WL 7-8 mm. Unlikely I suspect.

A good deep black colour with very little sternite dusting, face free of dust but a band of sharp edged white dust immediately below the antennae - C. ahenea WL 6-9 mm.

Black but not dense deep black, semi erect short thoracic hair of even length. Facial knob can project horizontally, but is variable. Sternite 1 with some dusting but others are glossy - C. antiqua WL 6-8 mm, usually a woodland fly.

Deep black colour, upper surface of facial knob horizontal, short dark thoracic hair, grey dusted frons - C. vicina WL 5-7 mm, often found on woodland edges.

Also possible but probably unlikely; C. nigripes, uncommon southern species WL 6.5-7.5 mm; C. sahlbergi, bronzy black with well dusted sternites, short brownish thoracic hair with longer fine black hairs - WL 6.5 mm. Found on Scottish highland moors.

But, once again, females can be difficult so this might be one for Roger Morris.

oxycera · #8 (**permalink**) 09-06-2010, 06:53 PM

Nice speculation, but as indicated earlier, it belongs to the Chrysogasterini.

peterbolson · #9 (**permalink**) 09-06-2010, 10:00 PM

I've had another look at this and now realise that it is a definate metallic green colour, which doesn't really show up in the photos I posted before so I've tried again.

I think John is right and that this belongs to Chrysogasterini, possibly Lejogaster metallina.
Haven't seen much evidence of Roger recently - do you think I should post it on the HRS website ? I'd like to get an answer soon so that I can release it.
Peter