Posted by Susan R Walter on 21-05-2006 21:55
#1
Is this
Helina sp? Female, 8mm, on flowering
Anthriscus sylvestris Cow Parsley, Preston Montford Field Studies Centre, near Shrewsbury, north west England, 16 May 2006.
Posted by Robert Nash on 23-05-2006 16:40
#8
Hi Susan Hard to use the key which early on relies on minute characters especially the presence of setulae on the underside of the radiocubital node (no glossary entry yet - a closeup photo would be great). However comparison with specimens in the collection here in Belfast (checked by Adrian Pont and Fonseca years back) indicates this may well be Helina duplicata (Meigen, 1826) a common species here and with you too. If you have a specimen I'll take a look at it or guide you through the key. How did you get it to Helina by the way? This is terrific progress.They are not easy without help in the early stages. Robert
Hint:p if you have Fonseca (RESL Handbook) :p:p take duplicata through the key backwards.
As was the case with Nikita's Pegomyia (gallery) this is well worth chasing up as reliably identified .... Am I repeating myself? Good galery candidate once the id is firmed up.
Posted by Susan R Walter on 23-05-2006 22:02
#9
Robert
Not sure if my magnification capabilities are up to this,
and I'll have to look up radiocubital node.:) I am not quite sure how to take this forward now - I will sit on it and think for a couple of weeks. Thank you for your kind offer to look at it, and I will send it to you in due course, but not before I've done a bit more work. I don't have the RESL Handbook - indeed, shamefully, I don't have
any of them. I think the problem has been, in the past, I've always wanted
all of them and never been able to make up my mind, and more recently, I can't afford these little luxuries:(
And how did I get to
Helina? Ahem...well...the process went something like this:
I had borrowed Colyer and Hammond from Birmingham Uni library, and thought I had better read the chapter on Muscidae on the train up to Preston Montford, where I had to return the book. I took notes focusing on the differences between the genera, fortunately before the train broke down and I had to get off at Coventry, lugging ten ton of reference books. The next day at Preston Montford I caught a dozen species of diptera and set about identifying them. Three quarters of them were, from the outset, clearly Muscidanthos of different species, which was useful because I could compare them and use a process of elimination as often as not. I started by checking wing venation and facial hair to establish whether they were Muscidae or Anthomyiidae. Then I checked things like number of stripes on the thoracic dorsum and number of visible abdominal segments. I didn't have access to the internet, so I was just picking up little hints and tips from a variety of relatively general reference books. I knew that the 4th vein on
Helina was supposed to 'curve gently backwards', a feature I thought this specimen might be exhibiting, and finally, the spots on the abdomen made me look at the picture in Insects of Britain and Western Europe. It does actually look quite like this if you know how to decode field guide illustrations, and indeed, the one in the book is
H duplicata, but I don't dare go to species level these days based on Chinery. I hope you are not too horrified:p
BTW, I often take things through the key backwards. I find it is quite a useful technique for clarifying something when you already have a fair idea what it is.