Hoverfly help!

[diggleken]

Hi,
Grateful for help with these two from yesterday please:
1/ Melangyna umbellatarum?

2/ Syrphus vitripennis?

Thanks a lot
Cheers
Ken

[Geoff F]

Ken, I had a quick look at this post before tea but then had to go out; and rather hoped that someone would have grabbed hold of this question and produced an answer before I returned.

The S. vitripennis looks good to me. This was a rather uncommon species for me but so far this year I am seeing more vitripennis than ribesii. Although females of both species are still a bit short. Plenty of unidentified males though.

Well, I suppose it's no good rambling while waiting for someone else; so I will have to consider your problem fly.

These are a tricky family and having run it through the ID Keys I appear to come up with Melangyna coei. The problem is that this is a European species although it does sometimes occur in the UK. The black dot in the scuttellum corners looks OK for a couple of species, but that rather large area of black on the frons is confusing me.

And according to the key M. coei fits perfectly.

So having lobbed in a silly answer, let's just sit back and wait for someone else to make a comment.

Meanwhile I will try the keys again.

[JRsbugs]

I had to go out too!

I've just run it through van Veen, I get Melangyna umbellatarum.

Now I have around 250 photos to download..

Janet

[Geoff F]

For M. umbellatarum, Stubbs gives a dark semicircle just above the antennae with some dusting above that but clear around the ocellar triangle.

He also warns of confusion between M. umbellatarum and M. compositarum/labiatarum.

So possibly Melangyna sp. is the safest option here.

And yes, I am also staring to fall behind in photo editing/species identification. Taking photos, I reckon, is the easy bit.

[JRsbugs]

Originally Posted by Geoff F

For M. umbellatarum, Stubbs gives a dark semicircle just above the antennae with some dusting above that but clear around the ocellar triangle.

I think those features are visible in the second pic? They are not mentioned in van Veen.

I had to assume there was a black stripe on the face, but I have had one which looks like this and comparing it they do look the same. Mine has more an elongated nose blob than a stripe but it still keys out with facial dusting. The early alternatives were wrong in other ways. i.e. it took me to two other species, guttata or triangulifera.

[Jason Green]

Evening all,

S. vitripennis is critically-confirmed by little microtrichae in the basal wing-cells - only a microscopial character.

Syrphus sp. and Melangyna sp. sound the most reliable here.

Take care,

Jason

[JRsbugs]

Originally Posted by Jason Green

Evening all,

S. vitripennis is critically-confirmed by little microtrichae in the basal wing-cells - only a microscopial character.

I don't think it's that difficult Jason. We have S. ribesii, females have all yellow or with just the base black hind femora. S. torvus has hairs on the eyes, these pics are clear enough to show there are no hairs even if the female doesn't have as much as males. S. vitripennis females have about 2/3 black on hind femora, as the other two species can be ruled out there is little doubt. S. rectus is a North American species and is not thought to be in Northern Europe according to van Veen because it falls within the range of variation of S. vitripennis, i.e. is probably the same species.

Syrphus sp. and Melangyna sp. sound the most reliable here.

Jason

Your original thoughts were for Melangyna umbellatarum, do tell why you have changed your mind Jason? Which keys are you using?

As said above, the alternative route regarding the stripe on the face led directly to two unlikely species so this had to be the correct route. The rest keyed to M. umbellatarum for females, where the wing microtrichia cannot be seen for certain the humeri is heavily grey-dusted for umbellatarum, and shiny for lasiophthalma, then the pale hairs on the thoracic dorsum cinch it. Taking the alternative at the wing stage leads to other features which appear not correct, both M. compositarum and labiatarum have a dull thoracic dorsum, halters a clear lemon yellow, and they are now thought to be the same species.

[Geoff F]

Stubbs also mentions M. umbellatarum having a yellowish front tarsus with a narrow black ring which was once used as an important identification aid.

But he considers this is too variable to be reliable.

[Anomalous]

Hi

I have come to this rather late, but the Syrphus does look good for vitripennis, with apparently bare eyes and extensively dark hind femora.

The Melangyna I would leave as labiatarum/compositarum, as the thorax is dull.

Both species are difficult from photos, of course. The Melangyna is very difficult in the hand, too!

Ian

[JRsbugs]

Originally Posted by Anomalous

Hi
The Melangyna I would leave as labiatarum/compositarum, as the thorax is dull.
Ian

That would be assuming the eyes are sparsely, or densely haired. They don't look to be haired but could have a minute amount.

Also assuming the halters are lemon yellow, I would call the spots lemon yellow and the halters are paler.

I would say the thorax is shiny, not dull but in a photo that can be difficult to tell.

It would also assume that the thoracic dorsum probably had some black hairs on the lateral margins, but they are sometimes absent and it's difficult to tell.

It also ignores the fact that the humeri is heavily dusted, or at least it looks to be to me and contrasts sharply with the "brightly shining postsutural depression" which is true for umbellatarum.

One more pointer for umbellatarum, the scutellum has a small black spot at the sides in the front corner.

I'm still opting for M. umbellatarum.