Diptera

Flies. About 150,000 species. Phytophagous, predaceous, or parasitic on other insects. Blood sucking species vector diseases.

One-Shot Wednesday—Proctacanthus fulviventris ovipositing

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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 Unfortunately, in the time it took to do this, the fly had already withdrawn her abdomen and was rapidly “sweeping” the tip of the abdomen back and forth over the hole—I presume to cover and hide it.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”!

REFERENCE:

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

More on Chalcosyrphus

/ Ted C. MacRae / 2 Comments

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?

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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

One-Shot Wednesday: Upside down bee fly

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Bombylius sp. cf. mexicanus | Scott Co., Missouri

This has got to be one of the strangest photos I’ve ever taken. Three weeks ago after visiting Sam A. Baker State Park (and photographing the scorpionfly featured in last week’s One-Shot Wednesday post), my dad and I visited a couple of sand prairie remnants in the Mississippi lowlands of extreme southeastern Missouri. I was hoping to see (and photograph) some individuals of the unique population of Cicindela scutellaris that occurs in that part of the state—apparently disjunct, this populations shows an intergrade of characters typical of subspecies C. s. lecontei to the north and C. s. unicolor to the south. I’ve photographed this population before, but those photographs were taken with a small (though quite good) point-and-shoot camera before I acquired my current dSLR camera setup.

Unfortunately, temperatures were quite cool that day, and no beetles were seen at either of the two locations we visited where I’ve seen good populations in past years. When I don’t find what I’m looking for, I start noticing other things, one of which was this very fresh-looking bee fly (order Diptera, family Bombyliidae) resting on the sandy ground. I’ve not really attempted to photograph many bee flies—they are as skittish and difficult to approach as the tiger beetles I adore but, unlike the latter, not a subject of my research and, thus, harder to justify spending inordinate amounts of time attempting photographs. This one, however, was sitting so nicely on the ground, and with no tiger beetles around to demand my attention I thought I would give it a shot (pun intended!). I carefully assembled my rig and slowly crouched down to attempt a photograph, but before I could get in position the fly spooked and tried to fly away. As it took off, however, it hit a plant and fell to the ground on it’s back. As it laid there,seemingly stunned, I got myself into position and took a quick shot to make sure I had the settings and exposure that I wanted. In that regard, I couldn’t ask for better, but of course what I really wanted was a photograph of the fly right-side up, resting on its feet rather than its back. Just as I was considering what to do next, the fly abruptly righted itself and flew away, leaving me with this single, rather unconventional photograph.

After perusing the bee fly pages at BugGuide, I was fairly certain this was something in the tribe Bombyliini, with the genera Bombylius and Systoechus being the likeliest candidates. Apparently the location of the r-m vein on the wing is an important distinguishing character between these genera, but I wasn’t quite sure about its location on the wing in this photograph. Nevertheless, some of the comments under the different species in these two genera suggested that members of Bombylius tend to be active as adults in the spring, while those of Systoechus tend more towards fall. I sent the photo to dipterist Joel Kitts at University of Guelph for his opinion—he confirmed that it belonged to the genus Bombylius and suggested its appearance was consistent with that of B. mexicanus—many thanks Joel!

Copyright © Ted C. MacRae 2012

More fly got eye!

/ Ted C. MacRae / 11 Comments

Here is another fly photographed during my recent visit to Argentina. I had little doubt when I saw it that it, too, was a member of the family Stratiomyidae; however, unlike the previous species this one was a far more cooperative subject for photographs. I have learned to carry a small utility tool in my pocket that contains an even smaller scissors—these have proven to be quite handy for gently snipping flowers or plant parts on which insects are perched without disturbing them. Holding these detached plant parts in front of the camera has several advantages, including the ability to photograph the subject while standing (or sitting) in a stable, comfortable position, providing more flexibility in choosing the background, and allowing me to “rest” some part of my hand or arm against some part of the camera or flash heads to “fix” the subject-to-lens distance. The fly remained quite calm through all these machinations, allowing me to focus on getting the composition, exposure, background, focus, and other technical aspects of the photos to my liking. Easier said than done of course, but a cooperative subject at least makes it more possible.

Psellidotus? sp. | Corrientes Prov., Argentina

I thought this fly looked an awful lot like our North American species of Odontomyia, so I sent the photos to stratiomyid expert Norman Woodley (Systematic Entomology Laboratory, Smithsonian Institution) for his opinion. Norm wrote back:

The stratiomyid fly…is in the subfamily Stratiomyinae, tribe Stratiomyini, which includes Odontomyia. I think that your fly is in the genus Psellidotus. Psellidotus is similar to another genus, Hedriodiscus…these two are easily separable in the Nearctic Region but the distinction becomes fuzzy in the Neotropics, especially in South America. We don’t have the species you photographed in the USNM collection. The majority of species in Psellidotus and Hedriodiscus in the Neotropics are very poorly known outside of their original descriptions.

Once again… fly got eye!

As before, this stratiomyid also exhibits stunningly patterned eyes, and like nearly all of the examples that I have seen the horizontal nature of the banding suggests an ability to see horizontally polarized light in similar fashion to many species of tabanids (Horváth et al. 2008). Again there seems to be a link between the ability to see horizontally polarized light and insects with aquatic lifestyles, as such visual capabilities have been demonstrated for a variety of other aquatic insects. While the biologies of most Neotropical stratiomyid species remain unknown, larvae of the subfamily Stratiomyinae are (like tabanid larvae) known to be aquatic (Brown 2009). Stratiomyine adults that exhibit these horizontal banding patterns may, like tabanids, also be able to see horizontally polarized light, which would be useful for finding mates and suitable sites for laying eggs.

REFERENCE:

Brown, V. B. 2009. Manual of Central American Diptera, Volume 1. NRC Research Press, 714 pp.

Horváth, G., J. Majer, L. Horváth, I. Szivák & G. Kriska. 2008. Ventral polarization vision in tabanids: horseflies and deerflies (Diptera: Tabanidae) are attracted to horizontally polarized light. Naturwissenschaften 95:1093–1100.

Copyright © Ted C. MacRae 2012

Fly got eye!

/ Ted C. MacRae / 15 Comments

While walking the grounds of my company’s experiment station in Fontezuela, Argentina, I encountered a massive European elm (Ulmus laevis)—its trunk enveloped by an unidentified woody vine with large, ball-clusters of small, green flowers. Despite their inconspicuous appearance, the flowers were highly attractive to insects, primarily honey bees and smallish, black and yellow vespid wasps. One of the wasps caught my attention—it was not quite as narrow as the others, and it flew a little differently. Closer inspection, of course, revealed that it was not a wasp after all, but rather a fly. I wasn’t sure what it was, but it was extremely flighty and wouldn’t allow me to get close enough even to attempt looking at it through the viewfinder—much less going for a composed shot. Now, if it were a tiger beetle I’d probably spend the next 2 hours “working” it to get that in situ shot. But, hey, it’s just a fly (with apologies to my dipterist friends)! I trapped it in a vial and collected some flowers and foliage from the vine with hopes of giving it a day or so to settle down enough to allow a few photographs in a more controlled environment.

Hoplitimyia sp. poss. mutabilis | Buenos Aires Province, Argentina

That proved more difficult than expected, and a few photographs was all I could get. Even after a day in the vial it was extremely flighty, and every time I released it onto the flowers in the white box I had setup it immediately tried to take flight. I decided it must at least be hungry, so I whipped up some sugar solution and painted a small amount onto one of the leaves, then placed the open end of the vial over the leaf to let the fly find the sugar. That worked—briefly! The fly paused just long enough to allow me to fire off a half-dozen shots or so while it drank and preened before once again attempting to take flight. No amount of coaxing back to the sugar could interest the fly—she’d had enough, and so had I. I thought the fly had a soldier fly-ish look to it (family Stratiomyidae), and this was confirmed by dipterist Martin Hauser who wrote:

It is a female Hoplitimyia, maybe mutabilis…but the species are a mess. There are at least two species in the US, and more in South America. They have aquatic larvae…

Fly got eye!

Among flies, tabanids and syrphids seem to get all the attention from insect photographers because of their contrastingly colored eyes, but this fly had every bit as much eye as those better known families! Considering how broadly across the order Diptera that one finds these stunningly patterned eyes—72 species out of 23 families according to Lunau & Knüttel (1995), an obvious question is what is their purpose. Considering that the patterns and coloration are often sexually dimorphic, it’s tempting to think it has something to do with mate selection, especially with their large size and resulting prominence. However, Horváth et al. (2008) presented evidence that the ventral eye surface of many tabanids are stimulated by horizontally polarized light. Such capabilities are common in aquatic insects, suggesting some function in locating water for finding hosts, mates and suitable sites for laying eggs. This still doesn’t explain why the patterns are often sexual dimorphic, although one can imagine that males and females experience different selective pressures for specific visual cues that could have an effect on the resulting color pattern. Comments from any dipterists that happen by this blog and have greater insight into this question would be greatly appreciated.

REFERENCE:

Horváth, G., J. Majer, L. Horváth, I. Szivák & G. Kriska. 2008. Ventral polarization vision in tabanids: horseflies and deerflies (Diptera: Tabanidae) are attracted to horizontally polarized light. Naturwissenschaften 95:1093–1100, DOI 10.1007/s00114-008-0425-5.

Lunau, K. & H. Knüttel. 1995. Vision through colored eyes. Naturwissenschaften 82(9):432-434, DOI: 10.1007/BF01133678.

Copyright © Ted C. MacRae 2012

Lord of the flies!

/ Ted C. MacRae / 23 Comments

I happened upon a rather interesting scene last week in a soybean field in northern Argentina (Chaco Province). This assassin bug (family Reduviidae) had captured and was feeding on an adult stink bug of the species Piezodorus guildinii—an important pest of soybean in Argentina and Brazil (where it is known by the common names “chinche de la alfalfa” and “chinche verde pequeño”, respectively). Assassin bug predation is always interesting enough itself, but what made this scene especially fascinating was the large congregation of flies surrounding and even crawling upon the predator and its prey. I had not witnessed something like this before, but it seemed clear to me that the flies were engaging in kleptoparasitism—i.e, stealing food. I’ve gotten into the habit of keeping a full set of extension tubes mounted on the camera with my 100mm macro lens—this not only provides the most useful (for me) range of magnification but also serves as a convenient and easy-to-use field microscope. Through the viewfinder I could see that there were at least two markedly different types of flies involved—more abundant, small, brown flies that I presumed (incorrectly, as it turns out) to be some type of drosophilid (vinegar fly), and a few larger, black flies that were completely unfamiliar to me. The flies were apparently feeding on fluids from the stink bug prey but also crawled all over the assassin bug as it fed. The assassin bug seem unencumbered in its feeding by the presence of the flies, but periodically it would slowly wipe its forelegs over its head to dislodge flies that had settled onto it. Just as quickly as they flew away, however, they crawled back.

The assassin bug, on the other hand, I recognized as very likely a species of Apiomerus—a large, exclusively New World genus known in North America as “bee killers” for their habit of sitting on flowers and ambushing visiting bees for prey. The prey selection behaviors of these insects, however, are more generalist than the name implies, as can be seen by these photographs. To verify my generic ID and possibly obtain a species ID, I sent some of these photos to Dimitri Forero at the Heteropteran Systematics Lab at University of California-Riverside. Dimitri is revising portions of Apiomerus (e.g., Berniker et al. 2011) and working on a general phylogenetic hypotheses for the genus. In the past he has been quite helpful in fielding questions from me about these bugs, and within a few hours Dimitri replied to inform me that the assassin bug was, indeed, a member of the genus Apiomerus, likely representing the common, widespread species A. lanipes (ranging from Panama to Argentina), based on its coloration, locality, and relative size. Update 12 March, 3:07 pm—After seeing the last photo in this post (which I did not send to him initially), Dimitri wrote to say the ventral abdominal pattern was not characteristic of A. lanipes. He asked about its size, to which I replied that it was about the same length but maybe a little less robust than A. crassipes (eastern North America). He later added, “I now think that this is A. flavipennis Herrich-Schaeffer, 1848. It is very similar to A. lanipes, but a lot smaller (lanipes is really robust), and with the abdomen with black and white patches, whereas in lanipes the abdomen is always black. I checked some series of specimens that I have here and, I am pretty sure now of the ID. I have material from Argentina as well. In some specimens that coloration of the corium varies, but the original description says it is yellow with a “hairy” pronotum, which fits very nicely your photos.” Apiomerus flavipennis is known from Argentina and Southern Brazil only.

Quite unexpectedly, Dimitri also noted that at least some of the flies could belong to the family Milichiidae. He first became aware of these flies after seeing a photograph of Apiomerus showing something similar and suggested Milichiidae online as a possible source for more information. This remarkably informative  website by milichiid expert Irina Blake, who dubs species in the family as “freeloader flies”, is a model for how websites dealing with obscure insect taxa should be organized and populated (and features on the home page a great photo of ant-mugging flies taken by our favorite myrmecophile). At any rate, I forwarded my photos to Irina and within minutes received her response that the bigger black flies most probably represent the cosmopolitan Milichiella lacteipennis and the smaller flies a species of the family Chloropidae (of “dog pecker gnat” fame) in the subfamily Oscinellinae, noting that she has seen similar (or the same?) chloropids in other photos as well engaging in kleptoparasitism.

Not long after receiving the first reply from Dimitri, I got another message from him with a link to a very interesting paper by Eisner and colleagues (1991), who recorded freeloader flies in Florida preferentially attracted to stink bugs and leaf-footed bugs (family Coreidae) being preyed upon by the orb-weaving spider Nephila clavipes. Olfactory stimuli were already suspected to be involved in attraction of milichiids and also chloropids (Sivinski 1985); however, Eisner et al. (1991) experimentally demonstrated that milichiid attraction was tied to specific components of defensive sprays in several pentatomid and coreid species (including P. guildenii, the prey species in this series of photographs). The defensive sprays of the bugs were generally ineffective at preventing predation by the spiders (and apparently this is the case for A. lanipes and other reduviids as well), thus serving as a signal to milichiids and chloropids not only of the presence of a food source but perhaps also assisting search for mates in a density dependent fashion (Sivinsky 1985). Milichiid attraction to hymenopteran prey, richly endowed with integumental glands themselves, has also been documented; the Eisner study raises the question whether these types of prey are also detected from chemical cues.

REFERENCES:

Berniker, L., S. Szerlip, D. Forero and C. Weirauch. 2011. Revision of the crassipes and pictipes species groups of Apiomerus Hahn (Hemiptera: Reduviidae: Harpactorinae). Zootaxa 2949:1–113.

Eisner, T., M. Eisner & M. Deyrup. 1991. Chemical attraction of kleptoparasitic flies to heteropteran insects caught by orb-weaving spiders. Proceedings of the National Academy of Sciences of the United States of America 88:8194–8197.

Sivinski, J. 1985. Mating by kleptoparasitic flies (Diptera: Chloropidae) on a spider host. Florida Entomologist 68(1):216–222.

Copyright © Ted C. MacRae 2012

Crazy Eyes 2

/ Ted C. MacRae / 4 Comments

Buenos Aires Province, Argentina | March 2012

While the eyes of this female horse fly (family Tabanidae) aren’t quite as striking as those of Tabanus lineolus (the wonderfully dimorphic males and females of which were made famous by Thomas Shahan and Ralph Holzehthal), they still managed to catch my eye as I was scouting for more pedestrian types of insect in a soybean field in central Argentina this past week. We know this is a female due to the separated eyes (males have larger eyes that meet at the middle of the head—supposedly the better to see females with); and by the obvious, blade-like mouthparts, which the females use to slice mammal skin so they can lap the blood that their eggs need for development prior to being laid while males forego specialized mouthparts and concentrate on using their huge eyes to look for females.

Female horse flies have well-separated eyes and distinct, blade-like mouthparts.

 

I suspect this individual had recently emerged from the soil (where many horse flies pupate) and was still hardening off, as she was very calm sitting on the leaf and allowed me to steady the leaf with one hand as I snapped a few photos with the other. I would have loved to have switched out the 100mm lens I was using and put on my 65mm 1-5X lens to really zoom in on those striking eyes. Unfortunately, I don’t think my field companions shared or understood my fascination with this little insect. If anybody has a clue about the identity of this species please let me know.

Copyright © Ted C. MacRae 2012