Thread subject: Diptera.info :: Helophilus continuus/affinis/pendulus?

Posted by Jens Nielsen on 23-07-2006 15:09
#1
I've made a few photo's of this hoverfly which is, as far as I've been able to determine from Collin's general insect field guide and some internet sources a Helophilus species (female), and I think either H. continuus/affinis/pendulus, probably the last one. Can anyone positively identify this species? The specimen was found in The Hague, The Netherlands on 9 August 2006.

When I've positively identified it, the picture will be put on the Wikipedia, so to avoid any perpetuation of a mistake, it's essential that it is not labelled with a wrong species name.

Thanks in advance,

Jens Nielsen
ex-biologist and Wikipedian
Edited by Jens Nielsen on 23-07-2006 15:19

Posted by Jens Nielsen on 23-07-2006 15:11
#2
top view:
Edited by Jens Nielsen on 23-07-2006 15:16

Posted by Jens Nielsen on 23-07-2006 15:12
#3
I'm having some problems posting this image, please bear with me if something fails here.
Edited by Jens Nielsen on 23-07-2006 15:14

Posted by Jens Nielsen on 23-07-2006 15:15
#4
here third picture showing head and antennae more clearly.

Posted by Tony Irwin on 23-07-2006 15:57
#5
Hi Jens
A fine female pendulus. No doubt.

Posted by Xespok on 23-07-2006 20:03
#6
The separation of the species within the genus, especially between pendulus and triittatus also puzzled me. After looking through many IDed images, it appears to me that the best feature is the top of the second abdominal segment. The two small spots in the middle are more pronounced and often have a different colour in pendulus. What other features separate the two species? Am I right that this is a reliable feature?

H. pendulus is much scarcer around here in Hungary, than trivittatus. I have not seen any other species in that genus.
Edited by Xespok on 23-07-2006 20:06

Posted by Kahis on 23-07-2006 20:24
#7
There's a very easy way to tell H. trivittatus apart from all other Helophilus: it has a all-yellow face while the other species have a black vertical stripe. This black band is well visible in your 2nd small image above. H. trivittatus is a large species and the pale areas on the 4th tergite (3rd large plate on top of abdomen) usually form a band. Other species have elongated spots almost touching each other.

The spots on 4th tergite are H. hybridus board and darker than pale areas on previous tergites.

H. pendulus has narrower, sausage-shaped spots on 4th tergite.

See http://www.veluwe...hilus.html for photos of these species.

This leaves us with H. affinis to describe. It is not rare in Finland, but I understand it is nor often seen in Central Europe. The females of this species are close to H. pendulus, the males closer to H. hybridus.