Thread subject: Diptera.info :: Sphaeroceridae I cannot ID
Posted by Gateside on 03-04-2022 09:35
#1
I took many photos of a small fly (4-5mm) moving about on ground debris in an area of lowland bog.
It is certainly a Sphaeroceridae. Using the key to Lesser Dung Flies by Brian Pitkin, I see it is a Copromyzinae (female).
Then I get into difficulties, because I cannot be sure if there is more than one row of postocular setae.
I think there is more than one row.
I have some bristles and other features which are difficult to be sure about in field photos. So I then started comparing illustrations, rather than using the key. I have concluded that some illustrations of the head side view are not reliable in places, because they show the shapes do not always match that from live specimens, or freshly dead ones. It seems to me that only the top-down view is reliable.
I am also puzzled by the mention of a length for Crumomyia nitida, when no other species has a length. Mine happens to fit in that range, but it doesn't look quite like nitida because that seems to have all black legs, while mine has shiny black femurs, and the tibae and tarsi are paler.
Can I conclude anything? Is an identification possible to species level?
Seen in Cumbria, UK.
Thanks.
Nigel.
Edited by Gateside on 03-04-2022 09:55
Posted by Gateside on 03-04-2022 09:37
#2
Here is a view of the legs. Strong bristles on mid tibia visible.
Edited by Gateside on 03-04-2022 09:47
Posted by Gateside on 03-04-2022 09:49
#3
Dorsum and head - main bristles are evident.
Posted by Gateside on 03-04-2022 09:50
#4
hind leg
Posted by Gateside on 03-04-2022 09:51
#5
side view of head. There might be more than one row of postocular bristles, but without better images, I cannot be sure.
Posted by Gateside on 03-04-2022 09:53
#6
side view of the front part of the thorax, showing some white patches (or shiny bits?)
Edited by Gateside on 03-04-2022 09:53
Posted by daveb21 on 05-04-2022 10:47
#7
Hi Nigel,
Definitely Crumomyia; size is mentioned as in general C. nitida is bigger than other Crumomyia, although I have seen large C. nigra (it isn't that) The leg colouring fits for C. nitida, the simplest way to confirm would be if you have a clear view of tibia 2 which usually has two antero ventral and three postero ventral setae, as the other likely species have only one of each. This would seem most likely to be C. nitida but it isn't conclusive from the images we have here.
Posted by Gateside on 05-04-2022 13:29
#8
Hi Dave
That is very heartening, because I was beginning to despair. (I took most of the photos using the wrong aperture, so that didn't help!).
I have found images of T2 to compare with the illustration figure 150, which is for C.nitida. It looks a pretty good match. (and I have a worse one for the side bristles). So that seems to stack the evidence for nitida quite well, I think.
Thanks Dave.
Nigel