One-Shot Wednesday—Proctacanthus fulviventris ovipositing

Proctacanthus fulviventris | Dixie Co., Florida

Today I spent the day just south of Florida’s “arm pit” to look for the state’s near-endemic tiger beetle Cicindelidia scabrosa (Scabrous Tiger Beetle). I first found this species last August on a white-sand 2-track through sand pine scrub habitat near Cedar Key Scrub State Preserve (Levy Co.). Although I was happy enough with the photographs that I got that day, the small spot of habitat that I found them in had yielded only a few specimens. My goal this time was to find the species in additional localities  to get a better idea of its precise habitat preferences and obtain a better series of specimens that more fully represents the range of variability exhibited by the species in its pubescence, color and elytral markings. By day’s end I would meet this goal, having found the species at four locations in Levy Co. and further north in Dixie Co. My first stop was actually in Dixie Co. near Lower Suwannee National Wildlife Refuge, where I found good numbers of individuals on a white-sand 2-track through pine scrub. A variety of robber flies (family Asilidae) were also seen along the 2-track, but I resisted the urge to photograph them because of the task at hand. Eventually, however, I came upon a female of this rather large species with her abdomen deeply inserted into the loose sand, surely in the act of oviposition. This was too much to pass up, so I set down the net, took off the backpack, and put the camera together. Unfortunately, in the time it took to do this, the fly had already withdrawn her abdomen and was rapidly “sweeping” the tip of the abdomen back and forth over the hole—I presume to cover and hide it. I snapped this first frame (the little bit of motion blur can be seen at the tip of the abdomen), but then I moved carelessly (not my usual habit) when scooting in for a closer shot. This spooked the fly and caused it to fly off, and I was left with this single image.

As much as I like robber flies, I can’t say that I’m well versed in their taxonomy. However, the large size (25–30 mm in length) and overall gestalt suggested to me that it belonged to the nominate subfamily, and cruising through online photographs eventually led me to Proctacanthus fulviventris. The individual seems to agree well with the description of this species provided by Hine (1911), including the bright yellow beard, black femora and red tibiae, and reddish abdominal terga. If my identification is correct, this species—like C. scabrosa—is also a Florida near-endemic whose distribution extends barely into southern Georgia. It’s dark coloration and light brown wings, combined with its large size, surely make it one of the more impressive-looking robber flies, and I’m sorry that I did not attempt to get more photographs of this species while I had the chance, as I did not see it at any of the other locations that I visited on the day.

Incidentally, by my interpretation the scientific name of this species translates to “yellow-bellied spiny-butt”!


Hine, J. S. 1911. Robberflies of the genera Promachus and Proctacanthus. Annals of the Entomological Society of America 4(2):153–172.

Copyright © Ted C. MacRae

14 thoughts on “One-Shot Wednesday—Proctacanthus fulviventris ovipositing

  1. Heckuva good one shot, Ted! As an insect photography enthusiast, robber flies are some of my favorites, but I don’t know much about them aside from their fierce hunting ability (I had one picking deer flies off of me last summer, kind of my hero). I’ve seen one (different species) exhibiting similar behavior, i.e. the abdomen pushing into the dirt, in the backyard up here in Western Mass. Thought it was oviposition, but good to have some confirmation.

    • Surely those are horse flies – the only large flies I can think of that would cause such a reaction from a horse. I’ve never heard of people or animals being bitten by robber flies – just other insects.

  2. Then your horses are as silly as some humans about these things, vsvevg, since these are not bees, and are completely harmless to mammals. Watch out if you’re a flying insect, though!
    Are you sure you’re not writing about either horse flies, or perhaps (also harmless) territorial male carpenter bees?

  3. Funny name for a rather ferocious predator, Ted! 😀 I’ve seen Robber Flies ovipositing on grass fronds a meter above the ground – it is interesting to know there is diversity even the selecting egg-laying site within the same Family – even though the larva ultimately end up in the soil.

  4. Pingback: The Weekly Flypaper » Biodiversity in Focus Blog

  5. Hi, Ted, I’m glad you like robber flies! Barry Knisley is here with six of his students from the 1970s (!) helping me with my study of Western Red-bellied Tiger beetles. Scientists like you and he have been so generous.


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