Is this Chrysotoxum cautum or elegans

[Geoff F]

On a short hedge just inland from the S. Devon coast path.

Not sure about this specimen. Thought the yellow abdominal bands look more like C. elegans and when I try to run it through the ID keys, C. elegans still appears to be a better match; although these images are far from ideal and I can't easily see any thoracic hair.




I'm in the correct area for C. elegans and although it is generally a woodland species I understand that they have been sighted along cliff tops in the SW.

But there are several very similar species; so other opinions would be welcomed.

ps. Very nearly missed this one as at first glance, without my glasses, I thought it was just another Syrphus ribesii.

[JRsbugs]

I would say Chrysotoxum verralli

Hoverflies - Diptera / Syrphidae / Syrphini

Janet

[bugbotherer]

Originally Posted by JRsbugs

I would say Chrysotoxum verralli

Hoverflies - Diptera / Syrphidae / Syrphini

Janet

I would say that's a good shout . Chrysotoxum verralli fits the bill in my book

[Geoff F]

Yes, C. verralli was on my list and to some extent the scutellum matches better, if it is a 'classic design' specimen. I'm not sure about the leading edge of the first black band. On one photo it looks rather narrow, like C. verralli but the other image appears broader with more of a curve to the yellow. Although this may well vary depending on the position and shape of the abdomen as the fly sits in different positions.

But the main thing that put me off C. verralli is that, as far as I am aware, it is limited to some selected areas of SE England while I am in the Salcombe area of S. Devon and C. elegans is, supposedly, found in Devon and Cornwall.

Otherwise, the advice in my book, appears to rely chiefly on the thoracic hair which isn't clearly visible.

ps. I've just done a bit more research on distribution and that seems to confirm that C. verralli is restricted to the SE, mainly Kent and East Anglia. A Plymouth based site said that C. cautum is rare in Devon but SW coasts are a stronghold for C. elegans, although never common.

So I'm still uncertain.

[Dogghound]

Possibly the info in the book is old? This species (which I agree on the ID) has spread north as far as south Lancashire as well as spreading west (although seems to be quite linear through the midlands). It remains fairly local, possibly due to habitat preference .

[tristanba]

I'd agree features best for verralli here, antennal segments 1 and 2 similar in length and narrow black band on second tergite

[Geoff F]

It was really just the location which originally put me off this species for an ID, but I suspose with all the traffic now it is quite possible for a wide range of bugs etc to simply fly into a van in one part of the country and escape somewhere totally different, let alone getting there under their own power.

So, just out of interest; I have been searching for any previous Devon records of this species and, quite frankly, I am disappointed at what I have found, or rather, haven't found. I was expecting to discover a central recording scheme where I could simply select a species and see all previous sightings records.

There are a frightening number of organisations which mostly appear to be run on a purely commercial basis and are looking for subscriptions but nothing which, as far as I can see, has much real practical value.

Anyway, enough of being grumpy for today! I have some friends who record bird sightings and I represent professional fishermen on our local Estuary Conservation Group so I'll see if I can find anything from them.

[Roger Morris]

Hello

There is a very comprehensive website covering hoverfly data. This is the Hoverfly Recording Scheme website at Hoverfly Recording Scheme - Index

There is a valid map for all species of Chrysotoxum. At the moment two species are likely to occur in Devon: C. elegans and C. cautum - but C. elegans is the more likely. I would not expect C. verrallii that far west. Curiously that species has not moved at all over recent years. In fact we think it is possibly declining.

My instinct for your photo says C. elegans but I am cautious - can you give some data please - that may help matters.

Regards

Roger Morris
Hoverfly Recording Scheme

[JRsbugs]

Hi Roger,

I had Chrysotoxum festivum last year and there's none on the map for my area near Lincoln. I had it verified by experts on diptera.info.

Diptera.info - Discussion Forum: Chrysotoxum festivum?

This would suggest the maps are not a totally accurate indicator as some just haven't been noticed.

Janet

[Geoff F]

After a bit of searching around I discovered the GBIF site which has proved useful for records of many other insect species in my area. They do show the occasional sighting of C. elegans in the exact same location Data Use Agreement - GBIF Portal[0].s=20&c[0].p=0&c[0].o=13445434

And eventually, after a bit more effort, I found a site which passed on sightings to the County Recorder; after getting the photos checked by an independent local expert. He agreed with C. elegans.

But it does still seem a rather long winded affair without any direct input or correspondence from 'casual observers' to the County Recorder.

I did find the Hoverfly Recording Scheme which is now a Bookmarked item for future reference.

Trying to decide what is or isn't worth recording from my various insect sightings is still a bit of guesswork and although I have sent details of a few various species I have omitted most of what I regard as probable common species. Eventually the go-between site http://www.devonwildlifetrust.org/index.php started requesting that any sightings should be checked by an expert before submission and the suggested boffins don't appear to be available; at least not without joining some specialist societies.

So, as this occurred towards the end of the main insect season I haven't bothered to look any further into the matter. Maybe I will have another think about these issues when warmer weather appears next Spring.