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Wasplike fly or wasp? - Physocephala sagittaria

Wasplike fly or wasp? - Physocephala sagittaria
Gainesville, Florida, USA
September 17, 2004
I thought this was a wasp but looking closer I believe I see a haltere.

Moved from Physocephala.

Species ID -- P. sagittaria
When I first saw this post, the patterning on the dorsum of the thorax and abdomen made me think "P. texana"...a species which is familiar to me and common in the west (as well as notoriously variable).

But looking closer, there were subtle discrepancies between this image and P. texana. First, the entire discal cell here is totally dark (vs. apically hyaline in texana). And the "T" shape on the frons is pure black (rather than red-brown), and wider than normally found in P. texana.

So I carefully ran this post through Williston's 1882 key here, as well as the keys in Camras (1957) and Camras (1996)...and arrived quite clearly at the outcome of P. sagittaria.

While the view in the image here does not show certain characters referred to in those keys (e.g. involving cheeks, facial grooves, and facial keel), if one "goes both ways" at the key breaks where such characters occur, one can eliminate all the alternatives based on range (most the alternatives occur outside the U. S.) or through contradictions with other characters visible here (e.g. the dark discal cell).

After arriving at the putative ID of P. sagittaria, I carefully read through the detailed 1882 description of "Conops sagittaria" given by Williston here, cross-referencing character-by-character with items visible in the image above. (I encourage all who may be interested to do so themselves.) The agreement is exceedingly excellent throughout!!

I then did the same with Van Duzee's 1927 description here of the synonymous species P. ruficornis to similar effect.

So, although I initially thought this was P. texana, I'm now thoroughly convinced it is P. sagittaria. That determination is also consistent with the range considerations. Florida is at the southern end of the recorded range of P. sagittaria. On the other hand, the range map for P. texana in Camras & Hurd(1) shows a broad swath of the southeast (from Texas to Georgia) excluded from texana's range. Also, it's mentioned on pg. 213 of Camras (1957) that a single Georgia record of Conops ochriceps Bigot (a synonym of P. texana) is likely an error, since P. texana "has not otherwise been found in the southeastern United Sates".

Conopidae fly
This one also seems to be a Conopidae like the one I posted on Sept 13.

Same but different:-)
Hannah's photo may be of a different genus, or at least a different gender. I still can't figure out how to tell Physoconops from Physocephala, but its one of those:-)

Glad you can narrow it down,
because there's a real dearth of information on the web! The one key is for Dutch species, I think.


This is Physocephala. The placement of a certain crossvein in the wing is different from that in Physoconops. I will prepare a picture soon with an arrow to point it out.
The Dutch key is practical in Northwestern Europe but quite a view of the North American genera are absent (e.g., [i[Physoconops[/i]). So, do not put all you trust in that key but use it for indication only!


Thank you, Paul,
I started to wonder whether I was just projecting. The difference I see is in the discal crossvein (the vein between the medial vein and the anterior cubital vein).
I began looking into this after taking a few photos last week of what I think is Physocephala (just posted, but I hope for better shots in a few days)
In Physocephala the discal crossvein is straight, and at a near right angle to the first branch of the anterior cubital vein. The distal part (away from wing base) of the discal medial cell is pretty much rectangular. For an illustration see Triplehorn & Johnson ((1) page 691, Fig. 34-15D).
In Physoconops the discal crossvein is slightly curved and more at an oblique angle to the first branch of the anterior cubital vein. The discal medial cell becomes narrower toward the wing base. For an illustration see photos for several species of this genus at AMNH Invertebrate Type Specimens (1).
For wing anatomy I used the Anatomical Atlas of CSIRO (1), as well as illustrations in Triplehorn & Johnson ((1)). Please let me know if I made any mistakes.

Thanks, Paul!
I will move to the guide.

I appreciate having a fly expert checking in, as it seems to be an underrepresented subset of insect-lovers!

That seems right. I even see one in the guide with similar wing coloration.