Help ID a hover fly please

[beeflysmith]

Hi, I would like some help IDing this hover fly if possible, fairly sure it is a Syrphidae and my best guess would be Eristalis (Interrupta?) based on comparison with other photo sites but would like some authentication if possible. Thanks
Nick

[JRsbugs]

That's correct.

The small squarish pterostigma is one defining factor here.

There are other features which can help though if that wasn't visible, as there are two more which are very similar, E. arbustorum and E. abusiva. In these you are relying on seeing close details of some leg colour or hairs, or the arista on the antennae to be sure.

Janet

[peterbolson]

I think the stigma extends to or just beyond the tip of Sc ( I enlarged and lightened the photos ) which would make it E.arbustorum or horticola. There is no well developed facial stripe and the hind metatarsus is as thick as the hind tibia so I think it's E.arbustorum.
Peter

[JRsbugs]

Originally Posted by peterbolson

I think the stigma extends to or just beyond the tip of Sc ( I enlarged and lightened the photos ) which would make it E.arbustorum or horticola. There is no well developed facial stripe and the hind metatarsus is as thick as the hind tibia so I think it's E.arbustorum.
Peter

E. horticola doesn't have a plumose face, anid if you look carefully at the thumbnail showing the face you will see a thin black central line going vertically, typical on both accounts (plumose with thin black line).



Also look at the hind tibia, if it was E. arbustorum there should be short black lashes on the apical half. This pic shows it to be yellow..



Maybe what you are seeing on the stigma is a bit of bleeding of colour?

[JRsbugs]

I should have posted this pic to illustrate the hind tibia.



I'll upload a pic of my E. arbustorum showing the hind leg better.

[JRsbugs]

Here's some pics of E. arbustorum, male and female



E. interrupta male

[peterbolson]

On seond thoughts I wondered if this was E.abusivus. Unfortunately we can't see the hairs on the aristae.

Using Stubbs key step by step :

face with central striae narrow or absent >
front and mid tarsi partly or entirely dark >
side of thorax & femora at most weakly dusted >
face with no central stripe = E.arbustorum OR
face with black stripe even if vague >
not furry >
hind tibia at least partly black >
hind metatarsus with black ground colour >
mid tibia yellowish or only obscurely darkened at apex = E.abusivus
mid tibia strongly black at apex >
stigma extends to or beyond tip of Sc, even if only as a pale brown extension to a dark spot ( see his drawings ) >
hard tarsus about as thick as hind tibia, face stripe poorly developed, wing clear apart from stigma = E.arbustorum

Peter

[JRsbugs]

OK, lets try another site which gives more info that Stubbs doesn't include..

Google Translate

[beeflysmith]

Hi guys, thanks for your efforts - it is obviously much more complex than I had anticipated, I'm very new to the world of Diptera and still have to learn the terminology - and also know what bits are important to help identify the various species etc. Reading through your comments I looked back at other photos and have attached 3 more higher res photos which may assist (the previous pics had been reduced to submit to a different website with a size limit!) So if these help I'd still love to know.
One last? question - I'm presuming this is a female and as such doesn't show signs of the paler orange 'saddle' on the thorax that are seen in the photos I've seen for arbostorum or horticola - are these markings very variable?
Thanks again for your time
Nick

[Jason Green]

Morning Nick,

Thorasic markings are variable according to species, and I wouldn't like to try ID'ing here with the evident complexity of arbustorum/horticola given Peter's key notes.

You can sex it by looking at the eyes - here, yours have a fair gap between them at the top, and as such is a girl. Males have bigger eyes that touch in the middle (or front with some Xylotini sp., such as Syritta).

Take care,

Jason