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At first glimpse, thought it was a Mydid :-) - Hermetia comstocki - female

At first glimpse, thought it was a Mydid :-) - Hermetia comstocki - Female
Off Rucker Cyn Rd, near junction with Arizona SR-80 between Douglas and the NM border, Cochise County, Arizona, USA
July 23, 2013
Found this on a nice, small, shrubby, yellow-flowered composite (didn't have time to key it). It was in the bowl of a large man-made livestock reservoir in the desert (originally bull-dozed...but becoming "naturalized"). See Google Maps link here.

At first glance in the field, the large antennae made me excitedly blurt out "Mydid!" I had mydids on the mind. After taking the single hasty shot seen here, it flew nearby to the ground where Alice Abela got a shot. It then flew up again and the violently gusting wind immediately carried it far beyond where we could reasonably track it (although we tried anyway :-)

After viewing the images on our camera displays, we realized it wasn't a mydid...but more likely a stratiomyid. (I was just off by the prefix, "stratio-" and an extra "d" :-)

Alice sent me a message this evening suggesting Hermetia comstocki. Knowing her, she's probably right. All the BG posts are from AZ, mostly Cochise County...and many are certainly a good visual match. Still, it would be nice to go through the MND key, and/or other references to check things out (at least for me). And/or to hear from an expert...ideally with mention of some characters that are diagnostic (and/or ref's I could follow up on).

I'm intrigued by the two stoutly hair-like protuberances at the tip of the abdomen (cerci, or...? See full-size version). Also, I'm wondering if this is a female? The eyes are dichoptic...but they appear dichoptic on every current BugGuide Hermetia comstocki I'm guessing that's probably not sufficient to diagnose this as a female.

Images of this individual: tag all
At first glimpse, thought it was a Mydid :-) - Hermetia comstocki - female At first glimpse, thought it was a Mydid :-) - Hermetia comstocki

Moved from Hermetia.

Stratiomyidae: Hermetia comstocki
Stratiomyidae: Hermetia comstocki; this is a female and what you see at the end of the abdomen are cerci.

Many Thanks, Norm
For the species ID and info on gender and cerci.

Moved from Soldier flies.

This keyed unambiguously to genus Hermetia in the MND(1). The elongate antennae (with the long, flattened "vane"-like terminal flagellomere) and the wing venation (with no m-cu cross-vein, and 4 veins emanating from the discal "fold"-like) make it clear this is Hermetia.

I'm fairly confident the species here is H. comstocki, and I'm thinking it's a female (see 2nd half of comment here)...but I'm hoping for expert confirmation on these two points.

Nice write up Aaron, and...
..I posted a series of images about the male showing it's typical posture which is to face downwards to the center of an agave, its antennae behavior and a macro shot of the eye. Click on:


Thanks, John
I like your contextual image showing the downward orientation of the Hermetia on the agave leaf...just as described in Alcock's nice paper!

BTW, I admire your boldness (and/or trust :-) in accepting my speculations about "mostly black thorax => male" vs. "mostly brick-reddish thorax => female" for Hermetia comstocki. I hope that hypothesis is correct...and that someone with more substantial experience & knowledge of the species (like Norm Woodley) will be able to verify it.

Maybe Woodley will stop by
and leave some comments explaining all this

Hi Aaron
We posted something relatively similar from Florida Canyon and got this response

Thanks J & J
I think Alice and Yurika are on the right track here. Using both my image and Alice's, I was able to work through the Stratiomyidae key in the MND(1) and clearly arrived at Hermetia. (BTW, the MND confirmed my suspicion that in Hermetia the eyes are widely separated in both sexes.)

While I wasn't able to find a key to nearctic Hermetia species, I was able to find Williston's original 1885 description of H. comstocki. For the most part, Williston's description agrees quite well with this fly...except that it indicates the thorax is mostly black, as in your post, Jillian's, and all the current BG posts except for Bob Behrstock's below:

Bob's post has a brick red thorax with just a narrow border of black surrounding the thin golden medial line, much like the fly Alice and I photographed. Martin Hauser confirmed Bob's post as H. comstocki, so I guess the "mostly black vs. dark red-brown thorax" is probably just intraspecies variation (or maybe Bob and our specimens were teneral, and more of the thorax might darken to black over time?). [Added later: Or color differences could be due to sexual reference to Alcock's paper in my later comment here].

By the way, I also checked Cole(2) (1969), who only mentions a few western species up to synonymy at that time: illucens, aurata, comstocki, concinna, and laviventris. According to James(3), both aurata and concinna have eyes does comstocki, though that doesn't seem very pronounced in the BG posts. Also, the 1965 catalog of NA Diptera by Stone et al(4) lists only 8 species, of which 5 are given for AZ, again: illucens, aurata, comstocki, concinna, and laviventris. The more recent catalog by Norm Woodley(5) may have more species. But comparing with images of these species currently on BG, it's probably a good bet this is H. comstocki.

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