Is this Hover fly Eristalis pertinax ?

[godders]

A new Hover fly to my Garden in Essex.

Is it Eristalis pertinax ?

Many thanks if you can confirm it for me, regards Nick

[Anomalous]

Hi

I don't think that this one can be definitely identified. There is no view of the face, to check for a dark stripe, and the pattern of dark and pale on the legs is not visible. I would say that it is not pertinax...it looks more like one of the smaller Eristalis, like arbustorum. I would leave it as a female Eristalis.

Ian

[godders]

Would this view help ?



thanks Nick

[Dillybythesea]

I'm glad you posted this one Nick, because I shall be very interested to know, too! In my page of notes about Eristalis I have it down that E. pertinax is recognised by the bi-coloured tibias of its hind legs (which I think I can see through the wings on your first shot) whereas the hind legs of E. tenax are uniformly dark. But I also have it down that Eristalis tenax has two rows of hairs on the eyes where others have one (and it looks as though yours has both vertical row and a horizontal row) so from what Ian says it looks as though I need another note about alternatives such as E. arbustorum, and a note about dark stripes?!

[JRsbugs]

This is Eristalis intricaria (intricarius here).

Sorry I meant interrupta!

[Matt Smith]

Going by the very minimal facial stripe, I would go for E.arbustorum.

[JRsbugs]

Originally Posted by Matt Smith

Going by the very minimal facial stripe, I would go for E.arbustorum.

The pterostigma appear to be small and squarish though. E. arbustorum also tends to have a white face, this isn't. The angle could be obscuring the stripe, which is often narrow anyway.

[Geoff F]

Nick. Some Eristalis species can be quite variable and easily cause confusion.

In this case, when viewing the enlarged photos, particularly the second image, there appears to be some fuzzy darkening of the stigma beyond the tip of vein Sc, even though the main dark spot is rather small.

E. interruptus should have a very sharply edged spot just before the Sc tip and clear beyond.

So based on that, I would suspect that E. arbustorum is the more likely.

[Matt Smith]

Originally Posted by JRsbugs

The pterostigma appear to be small and squarish though. E. arbustorum also tends to have a white face, this isn't. The angle could be obscuring the stripe, which is often narrow anyway.

Stubbs and Falk key E.arbustorum out as "face entirely pale dusted, absolutely no trace of a central black stripe". The colour white is specifically not applied to E.arbustorum, just as other colours are not applied to other species.

With rubbed E.arbustorum (ie those with a hint of a facial stripe), E. inerruptus is separated out using the stigma character "stigma reduced to a small dark spot before tip of Sc". E.arbustorum = "stigma extends to or beyond tip of SC, even if only as a pale brown extension of the brown spot". In the second picture you can clearly see the "pale brown extension" of the stigma extending well beyond the tip of vein Sc on the left side wing.

This appears to be a typical E.arbustorum to me.

[JRsbugs]

Interesting Matt, van Veen states arbustorum has face entirely whitish. Face stripe absent or very narrow, most old specimens have a narrow but distinct black stripe.

For interrupta, pterostigma square (including surrounding veins even shorter than wide.) it's position basal to the point where vein sc merges into the wing border. ... {I assume that to mean the width to include the veins at either side, no mention of a stain below the pterostigma for either species so one would assume that a stain is not important.}. Face: dusting dense, black stripe well-marked and relatively narrow.

I feel sure there is a visible stripe below the antennae! If you look at the right side flagellum (as we view it) it's much higher than the dark area below it.