orchid_b's picture

Helophilus trivittatus

Thought I would continue the discussion here. To sum up so far: I think it is possible to i/d trivittaus from above (without seeing the 'face' or more accurately facial stripe) from the colour of the frons just above the antennal insertion.

Here is an excellent photo showing the feature: http://www.diptera.info/photogallery.php?photo_id=7849.

The Falk plate shows this yellow area quite clearly from above. I think it is just a continuation of the facial stripe above the antennal insertion - maybe?

You can't always see this clearly in photos posted here, but if this is black it is usually obvious and I think rules out trivitattus. If it looks vaguely pale buff or yellow it might be just hidden in the 'dusting'.

Here is an interesting EOL photo labelled H. pendulus, which I think is actually trivittatus: http://media.eol.org/content/2010/03/24/05/88154_orig.jpg
Any thoughts?

There is one exception I have found so far: when the facial stripe is reddish-brown (as stated happens occasionally in Stubbs & Falk) this does continue to give a brownish insertion. The face is just as confusing in that case.

Why is this important? I think it is a good 'field character' that has not been mentioned elsewhere. The accepted wisdom seems to be that you can't i/d trivittatus without seeing the face, while I think this is as good if you can actually see it.

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orchid_b's picture

More misidentified pics?

I must put this one on here, but if I query it I am coming up against a world authority on Diptera, Chris Thompson (as with the one above), so yes I fear nobody , but no I'm not sure!

This is the lead photo for H. pendulus in EOL , and again I think it is trivittatus. Yellow above antennae, but much more obviously the characteristic grey-white 'inclined', bars that meet on tergite 4. Also no yellow hind margin to tergites. I rest my case.

http://eol.org/pages/748407/overview

Jamie from Briantspuddle

ophrys's picture

Photos

I think you are right on both counts.

This is one of the great problems of hoverfly photos on the internet...a huge number are wrongly identified, yet people take any picture as correct, so the misidentification problems get worse and worse. Don't even start to look at Syrphus!

One of the reasons to stick to sites like Steven Falk's...

http://www.flickr.com/photos/63075200@N07/collections/72157629586945825/

Ian
_________________

My Flickr photos...

http://www.flickr.com/photos/52163027@N02/

Dioctria's picture

Agreed

I agree, those two images are definitely male H. trivittatus.

David

orchid_b's picture

Thanks for the support. One

Thanks for the support. One of the forums should set up a wiki-identifier for new features like this as people notice them to pool knowledge more. I wonder if there is a bird one...just thinking aloud! I will contact the sites about the two pics and maybe enjoy hunting out some more.

Jamie from Briantspuddle

Dioctria's picture

Sorry

Sorry Jamie, but I dropped an email to EOL immediately after agreeing with you!

I didn't mean to steal your thunder, just thought that a glaring error on a site people probably trust should be corrected pronto. Or as ophrys says, one bad ID will lead to another...

David

Matt Smith's picture

Colour

The lemon yellow colour of the tergites and the overal size & shape are the best field characters for H.trivittatus if the face in not visible, all othe other Helophilus species are much more "orange", not yellow. Seeing the face just adds an extra level of confirmation.

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