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Found on Iris leaf in garden pond on 26-Oct-2014, in Ipswich (TM166450), Suffolk. I think this is a female Crumomyia notabilis. Is that correct?

Best wishes,
Martin

PS I have been convinced that a more probable ID is Borborillus uncinatus, but would appreciate any comments.

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dorsal view

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dorsal close-up

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dorsal abdomen

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lateral head

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thorax

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hind legs

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ventral view

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I am using the key published by Brian R Pitkin in 1988, Lesser Dung Flies DIPTERA: SPHAEROCERIDAE, Handbooks for the Identification of British Insects Vol 10, Part 5e, RES of London.
First, the key to subfamilies. I think the appended photo covers the characters needed to say this is in the Copromyzinae subfamily. The long scutellar marginal setae are gone, but I think we can see one resting on the abdomen, and the bases of 4 of them are visible.

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The wing is typical Copromyzinae. In the north temperate region, but not the tropics, each of the three subfamilies is easily identified by wing venation.

After that the family can be difficult. I don't think this is a Crumomyia. In the Nearctic key it could be Borborillus.

See http://www.dipter...d_id=15091

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Thanks John. In the Copromyzinae key in Pitkin 1988, the next question is about the postocular setae. A single row leads to Copromyza, Borborillus, whereas setae in at least two, usually irregular rows leads to Alloborborillus pallifrons and Crumomyia. I've appended a photo showing what I think are two rows of postoculars. Have I got that right?

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The next question is the number of well-developed setae on the postpronotal lobes (aka the humeral callus). Two leads to Alloborborus palliifrons and one to Crumomyia. I think there is just one well-developed seta among the several smaller ones.

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I think only one row is postocular, with the rest being occipital or something like that.

The name pallifrons suggests a pale frons.

Here is the Nearctic key (from the mid-1980s):

39. Genal bristle about one-half to three-fifths length of vibrissa. Head densely setose behind eyes, with postocular setae in numerous irregular rows. Mid tibia with four to five anterodorsal bristles. Wing crossveins often banded ... Crumomyia Macquart (including Fungobia Lioy)

... Genal bristle less than one-half length of vibrissa. Head with a single row of postocular bristles. Mid tibia with zero to two anterior and zero to two dorsal bristles. Crossveins not banded unless longitudinal veins also darkened ... 40

40. Scutellum with four long marginal bristles only. Hind tibia with an anteroventral bristle below middle. Frons entirely reddish brown to blackish ... Borborillus Duda

... Scutellum with at least six marginal setae, although some may be minute. Hind tibia with only weak anteroventral setae. Frons yellow or orange anteriorly ... 41

41. Hind tibia with a strong apicoventral bristle. Scutellum with four long and two to many tiny marginal setae. Frons completely pruinose ... Copromyza Fallén

... Hind tibia without a strong apicoventral bristle. Scutellum with 8-10 short stout marginal setae. Frons with ocellar triangle mostly bare ... Lotophila Lioy

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I'd disagree with John on the interpretation of "post-ocular" - Pitkin's figures indicate that his interpretation of the bristles is that any row behind the eyes is post-ocular, not just the ones immediately next to the eye margin.

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That is what confused me. I've attached a photo of Brian Pitkin's illustration.

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So, if there are indeed 2 rows of postoculars and just 1 well-developed postpronotal bristle, then the next question with a winged fly like this one is whether or not there are av setae about the middle of the hind tibiae. I think there are... see this photo:

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... that leads to a question about acrostichals and dorso-centrals and about the dusting and setae on some of the pleurites. The photo here shows the dorsal thorax. The choice is between 6 or more rows of acrostichals and 1 pair of dorsocentrals versus 4 or less rows of acrostichals and 3 pairs of dorsocentrals. It is quite hard to see the setae against the fine setulae, but I think the latter is the better fit, ie 4 rows of acros and 3 pairs of dcs.

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Associated with the 4 rows of acros and 3 pairs of DCs is the following: "anepisternum part shining, katerpisternum with few fine setae". The attached photo look consistent with that. The alternative would be "anepisternum dusted, katerpisternum with numerous fine setae".

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... and if all the above is right, the final decision is about the colour of the tibiae: dark brown to black, only slightly paler than the femora leads to Crumomyia notabilis, whereas yellow/brown, distinctly paler than femora to C pruinosa. The attached photo looks closer to the former to me, and hence to an ID of Crumomyia notabilis.

But is this right?

Please help!

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I would say this is Borborillus uncinatus from what I can see here.

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Thanks for this empeejay. But hasn't Borborillus only got the one row of postoculars?

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Please note that I had never seen a Sphaerocerid before finding this fly in the garden. All my comments are based solely on the RES Handbook 10.5e. I have been unable to find many photos on the web to clarify some of the problems I am having to arrive at an ID that seems (to me at least) consistent with the Pitkin key.

Here is a side by side comparison of photos of the head of this specimen with the diagrams for Boborillus uncinatus and Crumomyia notabilis in Brian Pitkin's key.

Best wishes,
Martin

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Looking more closely at the profile diagram from Pitkins for B uncinatus, there are 3 little hairs behind the postoculars! And the profile in the lateral view of the head looks a better fit for Borborillus than Crumomyia, too! So I'm now agreeing with empeejay that this is Borborillus uncinatus.

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From what I can see, I would agree with that last statement, but examining the specimen would of course be better.

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Thanks Paul!

I'd be happy to send the specimen to you if you had the time to examine it.

Best wishes,
Martin

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I will make the time. :)

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Thank you very much, Paul.
I will send this fly to you at Natuurhistorisch Museum Maastricht.

Martin

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|t

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Hi Paul, Did the fly arrive OK? Best wishes, Martin

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Oh dear, I thought I had replied already... :(

Yes, it arrived in perfect condition and identity is confirmed!

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Can we just clarify that it's identity is confirmed as Borborillus uncinatus? :)

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Yup

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Thanks Paul.
I will add a photo for this species to the Gallery. May I say how much I admire your efforts to promote Diptera and to help budding dipterists like myself.
Best wishes,
Martin