Beautiful hoverfly - Melanostoma scalare?

[Dillybythesea]

I was very taken with this today, and when I googled green halteres and Melanostoma scalare came up. Would that be it? She deserves a label for being so glam.

[JRsbugs]

If you can see it has well developed dust triangles between the eyes on the frons, then yes it is M. scalare. Unfortunately these are not showing sufficiently.

M. mellinum has a balckish shiny face, from the front view it does look black but again it can't be seen well. From the side view the face appears to have lots of dusting, but it can look this way on mellinum from the side as it highlights some dusting next to the eyes.

Green halters are not always reliable, some can be pale on scalare, and quite green on mellinum. The wings on scalare are a little longer than the abdomen, on mellinum the are about the same length as the abdomen. Again, can't tell.

Shape of spots is not always reliable either, but they are generally broader on mellinum.

On balance, the pale antennae and legs along with what appears to be dusting on the face I would say it's scalare as the face can be seen fairly well in the side-semi frontal view.

[Dillybythesea]

Thanks very much Janet. It's SO helpful to know the issues! I can say I think for certain the wings were longer than the abdomen, but I'm not sure what dusting means, I'll have to google that. Previously I assumed shading. Perhaps I'll add a couple more shots, if it's not pushing my luck?!

[JRsbugs]

The dusting is the powdery stuff on the face making it look pale. Looking at the frontal view the face looks more black.. even looking closely at the more semi frontal view it appears we are looking through the hairy stuff on the eye margins. This shows how tricky it can be.

Wing length can be tricky unless you have a shot with the wings closed and a shot directly from above or the side.

Leg and antennae colour can't really be taken as key points, but I have observed that scalare usually has both more yellow than mellinum.

I have lightened the frontal view you first posted, the face does appear to be dusted with triangular dust spots pointing to scalare.

[Dillybythesea]

Janet, as well as all those great things we agreed you are, you're also very kind! And I know now much more what I need to cover in the shots next time! Meanwhile I'll paste in two last shots because I hope they confirm the triangular dust spots you describe, and length of wings, but they might just show a blob of pollen and a trick of the angle!

[JRsbugs]

I remember how frustrated I was when trying to work out how to separate the two, it's not always possible as light, angle and wear can make it difficult apart from pregnant females distending the abdomen..

I've uploaded photos of both species females with a direct back view. You will see how the abdomen of mellinum is more rounded, and the obvious dust spots on scalare.

[Dillybythesea]

Got it - at last! That is SO helpful. I'm pasting it all in my ever-lengthening Fly Notes. You're just great. I hope you don't charge!

[JRsbugs]

Originally Posted by Dillybythesea

I hope you don't charge!

I'm free. ROFLOL!