More on Chalcosyrphus

Here are two more photos of the fly I tentatively identified as Chalcosyrphus sp. The first photo shows the all-black coloration with no trace of either steel blue highlights (seen in C. chalybea) or red abdominal markings (seen in C. piger). It also gives a better view of the enlarged and ventrally spinose metafemora. The second photo shows the holoptic (contiguous) eyes that make me think this is a male individual (if, indeed, this is true for syrphids as with tabanids).

I’m hoping that posting these will provide any passing dipterists with the information needed for a firmer ID (and possibly an explanation of the purpose of those intriguingly modified hind legs).

Lateral view showing black abdomen with no trace of red (except what appears to be a parasitic mite).

Do the holoptic eyes identify this as a male?

Copyright © Ted C. MacRae 2012

T.G.I.Flyday – Chalcosyrphus?

When I was an entomology student, I learned that flies in the family Syrphidae are called “hover flies,” due to their habit of hovering in front of flowers, and that the larvae are predators of aphids. As is the case for nearly every other group of insects, I now know that there are exceptions–often many—to the typical rule, and the fly shown in the above photograph is a perfect example of such. Being a beetle-man (and a wood-boring beetle-man, at that), I don’t generally notice flies unless there is something unusual about them. This fly was seen last summer at Sam A. Baker State Park in southeastern Missouri on the trunk of a very large, recently wind-thrown mockernut hickory (Carya alba) tree. I had never seen a fly quite like this before, but everything about it suggested an intimate association with dead wood, including its relatively large, hulking, black form and the way it repeated returned to and landed on the trunk of the dead tree each time I disturbed it. It instantly made me think of robber flies in the subfamily Laphriinae, which includes Andrenosoma fulvicaudum and many species of Laphria that, as larvae, tunnel through dead and decaying wood where they prey upon the larvae of wood-boring beetles. While it was quite obvious that the fly in the photo was not a robber fly, imagine my surprise when I eventually determined it to be a member of the family Syrphidae. For now I’ve provisionally settled on the genus Chalcosyrphus, although it lacks the steely blue cast exhibited by the only all-black species of the genus—C. chalybeus—shown on BugGuide. Another species, C. piger, looks very similar but seems always to have some red on the abdomen, which this individual definitely lacks. Perhaps the related genus Xylota is also a possibility, although the “gestalt” does not seem to quite match that of any shown on BugGuide. Most interesting for me are the distinctly enlarged and toothed metafemora, which along with the correspondingly curved tibiae suggest some predatory function, but the literature that I have seen makes no mention of such, but rather that the adults feed on pollen. My hunch about its association with dead wood does seem to be true, although it now seems the larvae are saprophages rather than predators within the wood, as I first imagined.

Copyright © Ted C. MacRae 2012

Hover fly on mallow flower

I’ve mentioned before my reluctance to take random “bug on a flower” photos, but the colors of this hover fly (family Syrphidae) and the mallow flower (Malvaceae, possibly Abutilon pauciflorum) on which it was sitting were enough to capture my interest—a rare offering from this blog to dipterophiles. Even though I’m a beetle man, I’ve had reasonably good success identifying the varied insects across several orders and families that I’ve photographed at the Reserve. This one, however, has me a little stumped. I searched the syrphid gallery at but didn’t find a good match, the most similar being the Old World species Episyrphus balteatus. My best guess is something in the tribe Syrphini. Morgan? Keith? Phoridae?

Photographed last month at  in Buenos Aires.

Copyright © Ted C. MacRae 2011

Bichos Argentinos #1 – Eristalinus taeniops

Eristalinus taeniops - a hover fly in the family Syrphidae

It figures that perhaps the most striking insect I saw at La Reserva Ecológica Costanera Sur in Buenos Aires, Argentina would be an introduced species, as the area itself is a man-made reconstruction of the wet Pampas grasslands endemic to coastal areas of the Rio de la Plata.  My identification of this fly as Eristalinus taeniops is based on its great resemblance to the many online photographs that exist from both South America and the U.S. and also the Old World where it is apparently native.  I found no more authoritative sources with which to confirm the ID, so this online comparative will have to do (muscophiles feel free to comment or correct). 

According to BugGuide, E. taeniops is a recent import to the U.S. from Africa, and in fact it has apparently successfully invaded much of the world.  I suppose most folks will be inclined to forgive the fly for all this because of its strikingly patterned eyes, which I would have dearly loved to have gotten in tight for a closeup.  This shot with the 100mm lens dialed in to the max (and only slightly cropped for composition), however, was the only one I managed – the fly bolted as I quickly tried to switch to the 65mm lens, and although I saw two more individuals afterwards, I couldn’t get anywhere close to them in the day’s heat.  Eyes notwithstanding, the species is a near perfect mimic of a honey bee, making one wonder what selective pressures drove the development of these fantastically contrasting eyes.

Copyright © Ted C. MacRae 2011