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mystery pollinator for the rare Canadian River Spiny Aster (CRSA) - Exoprosopa caliptera

mystery pollinator for the rare Canadian River Spiny Aster (CRSA) - Exoprosopa caliptera
Raton Mesa/pass,Trinidad, Las Animas County, Colorado, USA
September 10, 2006
Size: 3 cm X 1.2 cm

Images of this individual: tag all
mystery pollinator for the rare Canadian River Spiny Aster (CRSA) - Exoprosopa caliptera mystery pollinator for the rare Canadian River Spiny Aster (CRSA) - Exoprosopa caliptera mystery pollinator for the rare Canadian River Spiny Aster (CRSA) - Exoprosopa caliptera


Revisiting this post...after 8 years
I was recently studying differences between Exoprosopa dorcadion and E. caliptera and came upon this interesting post.

Marie, I hope you don't object, but the images posted herein in 2007 had over 50% of their area blank I cropped and adjusted the images to make them more useful for most BugGuide viewers (who can only view a 560 X 560 pixel size verison of any posted image). Note that in cropping the images, the magnification of your original full-size images was not reduced, so BG editors and experts can still see the full detail present in the originals. (And if you wish, I will restore the originals immediately if you so request.)

I was puzzled and intrigued by this post, as it appears to me to have wing infuscation that mixes characters of both E. dorcadion and E. caliptera. To faciliate study, I made a collage of cropped wing views for comparing Marie's specimen, E. caliptera (from the MND(1)), and E. dorcadion (from the MCZ(2) type)...see the image and accompanying remarks in post thumbnailed below:


So species ID here seems tricky, as characters of both species are present...though I'd say overall E. caliptera seems the best call (if one is to be made, I suppose it could be some other taxon). Hartmut suggested E. caliptera in two earlier comments below, though he also referred to an E. dorcadion image in his later comment of 7/19/2007 (with subject heading "Variety"). It's not clear how this post ended up under E. dorcadian...I couldn't find any "Moved" comments among the comment threads associated with the 3 images in Marie's post.

from California's Transverse Ranges: Mt. Pinos .

Hello Marie,
I've e-mailed some more information to Herschel, including a brief description for both E. caliptera and rhea (with a habitus drawing of rhea). I'd forward it to you but you e-mail isn't given on the contributor page.
Yours looks closer to caliptera though; rhea is described as a "striking black species with a red-orange pilose collar".

email comtact
If you would like to send me anything I can be reached at

take care, Marie

Looking at the left wing
in the far right photo, I can "kinda" see, or at least imagine a third submarginal cell. If so, this would make it Exoprosopa.
However, though quite close to E. caliptera in wing pattern, the apical hyaline field in that species touches all three submarginals; not so in the present fly. Herschel has probably looked at specimen of these, and may be able to tell us whether there is such variation in this species.

I did not have a specimen of that species in my current boxes at home. I will be at the museum on Monday however. I will check for variation. I think you can see the separate distal cell on the wing with enlarged shots on this one. And the dark margin of the pattern parallels the vein line. I don't think any Poecilanthrax have the strongly delineated pattern of this fly or that apical cell separation. Most have very smoky wings or dot patterns with smoky fore edges. In the rockies, of course, there could be some others but I doubt there is one that matches E. caliptera that closely.

The images on my website key are from Hull mostly.

And a wonderful website you built, Herschel!
Since I live in the western US, I purchased Hull's book recently, and also use the key to genera in Cole & Schlinger.
By now, after having looked more closely, and read your comments, Herschel, I see three submarginal cells.
Marie could take a look at the wing venation for E. caliptera on your site.
Another remarkably similar species, including abdominal markins, and wing pattern, is E. rhea (with distribution listed as AZ, NM, TX) Yet, there are also some differences. I'd post a copy of the illustration for rhea, but wonder about copyrights.
Marie, I suggest you send your images to Neal Evenhuis, Bishop Museum, Honolulu, Hawaii. His specialty is bee flies.

I think it would be okay to send the wing image to Marie directly. And to me. I don't put images on my website that are not out of print or in journals that are still available generally to the public. I will see what E. rhea looks like somewhere. Though it will effect only you west and southwesterners.

Please let me know if you find something out of date on the keys otherwise.

Thank you again
I found an email address for Neal Evenhuis at the museum and sent an email with the pictures to him. I am hoping Herschel Raney will be able to give me a difinitive on Monday when he goes to the museum :)
I did mention the possibility of E. rhea as well in the email to Neal.
Thank you all again so much, Marie

bee fly
i saved the picture and enlarged it... i think i can see the third submarginal cell... but it could be that i just want to see it. after looking at the Hull wing again, i will admit the pattern is not an exact match, but oh so close, and i do not know about individual variation on this one.

Family Bombyliidae -
looks like a Poecilanthrax Osten Sacken, don't know what species.

bee fly
just a guess... but those wings look like Exoprosopa caliptera, however, i am far from an expert.

I had been considering Exoprosopa,
and I can see your point re. wing pattern, but there are also differences. Exoprosopa has three submarginal cells, I can only see two in these photos. Head and antennae look more like Poecilanthrax to me (I'm using Hull, (1)). I'm not an expert either, just looking at the definitions. Yet, I might overlook something.

Edward is becoming an expert. This is the distinctive wing pattern of E. caliptera. Fairly common, I think, in the rockies and the east.

This fly was not harmed and i
This fly was not harmed and it died naturally in our lab here at Trindad State Junior College. I am working on research pertaining to the decline of Canadian River Spiny Aster. Looking specifically in this study for a loss of a pollnator, this fly seems to be a good pollinator, however it seems to be rare.
Thank you in advance for any help,

bee fly
I doubt whether your bee fly is the main pollinator along side the river system. As you say, although it is a good pollinator it is rare. Beeflies are not generally noted in large numbers. You may try looking at hoverflies (i think you refer to them as sunflies in the US/Canada: Syrphidae) or even more likely bees and wasps (Aculeate hymenoptera). These, generally, are very good pollinators. If there has been a large shift in the meanders of the river and a loss of bare sandy ground or cliffs then id consider the possiblity that bees adn wasps are possibly the pollinator. Many are fossorial (gorund nesting) and dig holes in sandy ground or cliff faces.
You could try and ask a specialist in aculeate hymenoptera if they know of a species that specifically feeds on Aters. Lots of bee species are specilaised and collect pollen and nectar from one type of flower such as Scabious or Asters. This will help you eliminate or focus your attention onto a species or species group.
I hope this helps a bit with your research.
Andy Jukes

Good points,
may I also suggest a book containing reports on recent work in pollination biology: Plant-Pollinator Interactions ([cite:95013]).

CRSA pollinators
All good suggestions and Thank you, I will see if we can get Plant Pollinator Interactions on inter library loan.
The name of this Aster is miss leading, it is found in only three places in Colorado and it is always in the aluvial fan areas of cliff drainage in sandy soft soil below but not in Ponderosa Pine areas and above 6,000 feet altitude usually not near a river except maybe in an arroyo(sp?).
We have recovered about fourteen different visitor insects to this aster but this is the only one that has been found to have significant levels of CRSA pollen. There have been some bees and beeflies that seem to even either avoid the CRSA for some reason or just do not see it due to perhaps a UV level that is not visible to the other potential polinators. this fly seems to spend most if not all of it's time at the CRSA, this is why I am focusing in on this fly's ID and if I can do that I can hopefully see what it's habitat and behaviors are and move forward from there.
There is a bee fly, I think it is Systoechus Solitus, that appears to be a nectar robber to the CRSA so I am also looking at the possiblity of loss of an attractant due to nectar robbing and thus influencing polination as well.

Check into the forums here
You may want to post something about your research, with an eye to obtaining photos of insects on Canadian River Spiny Aster from other Bug Guide contributors. I'm not all that familiar with most forums, but am fairly sure there's one to address your needs.

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