Maddening mutillid

Traumatomutilla graphica (Gerstaecker, 1874) | Parque Nacional Chaco, Argentina

During my stay in Corrientes, Argentina, I had two distinct biomes to explore—the relatively moist “Selva Paraguayense” to the east in Corrientes Province (a southern adjunct to the Atlantic Forest of southeastern Brazil, and home to the cryptic longhorned beetle that I featured in Desmiphora hirticollis: Crypsis or Mimicry?), and the drier “Gran Chaco” to the west, home of the insect featured in today’s post. Precious few remnants remain of the original Gran Chaco, which once covered nearly 1 million square kilometers in northern Argentina, Paraguay and Bolivia and the best example of which can be found at Parque Nacional Chaco in north-central Argentina. I’ve already mentioned that conditions are typically quite dry by early April in northern Argentina, and this is especially true of Chaco Province, where droughts during the months of January through March are common. As a result, I didn’t expect to see much insect activity during my visit last month. For the most part this was true, but one insect I did see at several points along the trails through the park was this rather large velvet ant (order Hymenoptera, family Mutillidae). Not an ant, of course, but a true wasp, these insects must be treated with respect as they are capable of delivering a painful sting. This, combined with their ceaseless, erratic wanderings makes them incredibly difficult to photograph. However, with few other insects to see, I thought I would spend the time and effort to see if I could get some good field photographs of this very attractive species. I spent about half an hour attempting to photograph it by panning through the viewfinder while getting closer and adjusting the focus on the move, and then firing shots when I thought I might be close enough and had the individual more-or-less within the frame. This was wildly unsuccessful, as I had only a 3-ft wide path within which to work and had to constantly get up to block its escape into the adjacent vegetation. Moreover, it was exhausting! The constant moving and body contortions while in crouched or kneeling positions used muscles I didn’t even know I had (but was well aware of the following day by their soreness!). Out of the countless shots that I fired, these two photographs are the only ones that I consider worthy of posting—pretty good, but not great.

The distinctive color pattern is diagnostic for the species.

According to Kevin Williams (many thanks!), the distinctive color pattern readily identifies this individual as Traumatomutilla graphica (Gerstaecker, 1874). Nearly the size of our common eastern North American Dasymutilla occidentalis (a.k.a., cow killer), the bold, conspicuous patterning surely must serve as advertisement of its powerful defensive capabilities—I know I was deterred from trying to handle it. Kevin mentions it as a “great find!” and that the male of the species is still unknown, and I could find nothing about the biology of this species. However, mutillids in general are known to develop as external parasitoids of various wasps, bees, beetles and flies, the excessively long female ovipositor enabling piercing of host nest cells before injecting their powerful venom and placing the eggs (Hogue 1993).

REFERENCE:

Hogue, C. L. 1993. Latin American Insects and Entomology. University of California Press, Berkeley and Los Angeles, 536 pp.

Copyright © Ted C. MacRae 2012

Aglaoschema rufiventre in Chaco, Argentina

Aglaoschema rufiventre | Chaco Province, Argentina

I’ve mentioned a few times that April is not a very good time to look for beetles in northern Argentina, as the months preceding April are typically hot and dry. September through January would be a much better time, especially to look for the wood boring beetles (families Buprestidae and Cerambycidae) that I am so fond of. Still, if I am in Argentina in April then I must look for beetles in April, and while I didn’t see a single buprestid during my week in Corrientes and Chaco Provinces last month I did a fair number of cerambycid beetles on stands of goldenrod (Solidago chilensis) at a few localities in Chaco Province. One particularly common species was Aglaoschema rufiventre, a beautiful metallic green species with, you guessed it, a red abdomen. Aglaoschema is a rather large (27 species), exclusively Neotropical genus whose members superficially resemble the diurnal, brightly colored species of the tribe Trachyderini but actually belong to the tribe Compsocerini. Most of the species occur in Brazil, but six extend further south into Argentina. Of these, A. rufiventre most resembles A. haemorrhoidale and A. ventrale but is distinguished by its subcylindrical antennal scape—or first segment (clavate in A. ventrale) and non-roughened elytra (roughened—or “asperate”—in A. hemorrhoidale) (Napp 2007). No hosts have been reported for A. rufiventre (Monné 2001), so my finding of adults on flowers of S. chilensis seems to be the first reported host association for the species.

The species name refers to its “red belly”

I photographed several of these beetles on S. chilensis flowers at two locations in Chaco Province along Ruta 16 west of Resistencia, but I was generally unsatisfied with how the photos turned out. The combination of the beetles’ metallic sheen and the bright yellow color of the flowers made getting the right exposure and lighting difficult—I either blew out the yellow on the flowers or ended up with deep shadows on the beetles. One morning I encountered this female sitting on the seed head of an grass unidentified grass. Torpid from the cool temperatures and covered in morning dew, she was a most cooperative subject, and the colors of the seed head turned out to be much more complimentary for photographing the beetle that the bright yellow goldenrod flowers.

REFERENCES:

Monné, M. A. 2001. Catalogue of the Neotropical Cerambycidae (Coleoptera) with known host plant—Part I: Subfamily Cerambycinae, tribes Achrysonini to Elaphidiini. Publicações Avulsas do Museu Nacional 88:1–108.

Napp, D. S. 2007. Revisão do gênero Aglaoschema Napp (Coleoptera, Cerambycidae). Revista Brasileira de Zoologia 24(3):793–816.

Copyright © Ted C. MacRae 2012

Desmiphora hirticollis: Crypsis or Mimicry?

During my stay in Corrientes, Argentina last month, I was invited to spend the day with a colleague at his “camp” in Paso de la Patria. Located on the banks of the massive Rio Paraná at its junction with the Rio Paraguay, this small resort community boasts large tracts of relatively intact “Selva Paranaense,” which together with the Atlantic Forest in southeastern Brazil forms the second largest forest ecozone in South America outside of the Amazon. As my colleague skillfully prepared matambre, chorizo, and vacío (typical cuts of meat in Argentina) on the parilla (wood grill) at his camp, I explored the surrounding forest for insects. Early April is late in the season, and with generally droughty conditions in the area for the past several months there were few insects to be found. My luck improved, however, when I came upon a small area with stacks of fresh cut logs from recent wood cutting operations scattered through the area. Wood boring beetles (families Buprestidae and Cerambycidae) are often attracted to such wood piles, so approached each one slowly to look for day-active species of these beetles. After inspecting several piles without seeing anything on them, I began carefully turning over the logs to look for nocturnal species that tend to hide on the undersides during the day. Shortly I came across this highly cryptic species of cerambycid, and further searching revealed a fair number of these beetles hiding within the dozen or so log piles that I examined.

Desmiphora hirticollis on freshly cut guayabi (Patagonia americana) | Corrientes Prov., Argentina

I instantly recognized the genus as Desmiphora, an exclusively New World genus characterized by the presence of fasciculate tufts (or “pencils”) of erect or suberect hairs. Most of its nearly 50 species occur in Brazil, but two species extend as far north as southern Texas (Giesbert 1998). One of these is Desmiphora hirticollis, a widespread species found as far north as Corpus Christi, Texas and as far south as Bolivia and Argentina. I thought these beetles looked an awful lot like that species, and I later confirmed its identity as such due to its piceous (glossy brownish black) integument and the presence of small black pencils just before the elytral apices.

Adults are nearly impossible to see from overhead due to cryptic coloration…

The wood piles contained logs from several tree species, but all of the beetles that I encountered were on logs of guayaibi (Patagonula americana), a member of the family Boraginaceae and a characteristic component of Selva Paranaense (also an important timber species in Argentina). The number of individuals that I found and their occurrence only on guayaibi suggests it serves as a larval host for the beetle. Duffy (1960) described the larva from specimens collected out of Sapium sp. (family Euphorbiaceae), but in Texas this species is collected most often on Cordia spp. and Ehretia anacua (Rice et al. 1985)—both in the family Boraginaceae—with adults having been reared from Cordia eleagnoides (Chemsak & Noguera 1993).

…while the hair tufts may function in obscuring the body outline…

It seems obvious that coloration of the beetle and its pencils of hair function in crypsis. From overhead the beetles are almost impossible to discern as they sit motionless on the similarly colored bark of their host trees. Even in profile or oblique views where the body becomes somewhat more visible, the pencils seem to break up and obscure the outline of the body. I wonder, however, if crypsis is the only function of the pencils—Belt (2004) described the strong resemblance of another species in the genus, D. fasciculata—a similarly penicillate species, to short, thick, hairy caterpillars (insectivorous birds often refuse to prey upon hairy species of caterpillars). That species can be seen sitting openly on foliage during the day, while D. hirticollis seems to be strictly nocturnal; however, cryptic and mimetic functions need not be mutually exclusive, so perhaps for this species the pencils function a little for both.

…or perhaps even mimicking ”hairy” caterpillars.

REFERENCES:

Belt, T. 2004. The Naturalist in Nicaragua. Project Guttenberg eBook.

Chemsak, J. A. & F. A. Noguera.  1993.  Annotated checklist of the Cerambycidae of the Estacion de Biologia Chamela, Jalisco, Mexico (Coleoptera), with descriptions of new genera and species.  Folia Entomológica Mexicana 89:55–102.

Duffy, E. A. J. 1960. A Monograph of the Immature Stages of Neotropical Timber Beetles (Cerambycidae). British Museum of Natural History, London. 327 p.

Giesbert, E. F. 1998. A review of the genus Desmiphora Audinet-Serville (Coleoptera: Cerambycidae: Lamiinae: Desmiphorini) in North America, Mexico and Central America. Occasional Papers of the Consortium Coleopterorum 2(1): 27–43.

Rice, M. E., R. H. Turnbow, Jr. & F. T. Hovore. 1985. Biological and distributional observations on Cerambycidae from the southwestern United States (Coleoptera). The Coleopterists Bulletin 39(1):18–24.

Copyright © Ted C. MacRae 2012

More fly got eye!

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

Traffic Jam Treehoppers

Sometimes photo opportunities come at the unlikeliest of times. A few weeks ago while traveling back to Corrientes, Argentina from neighboring Chaco Province, I came upon traffic at a standstill just a few kilometers from the towering Gral. Belgrano bridge that spans the massive Rio Paraná to link Chaco and Corrientes Provinces. People were already getting out of their cars and walking around, suggesting a wreck closer to (or on) the bridge had completely shut down the highway for the time being. Somebody said they heard it might be another 45 minutes before it could be opened. What to do now? It was the end of my last day after a week of insect collecting/photographing in the area, and the last thing I wanted to do was spend the evening sitting on a divided highway with nowhere to go and nothing remotely interesting to look at…

Enchenopa gracilis (Germar, 1821) | Chaco Province, Argentina

…or so I thought. While scanning the highway right-of-way to see if there might be anything possibly interesting to look at, I spotted a small clump of woody shrubs down the embankment and across the erosion gully before the fenceline. I looked around—everybody was out of their cars with the engines shut off, so I grabbed my camera (not really sure why) and started walking towards the shrubs while looking ahead every now and then for any sign that people were getting back in their cars and moving again. I reached the shrubs and saw they represented something in the mallow family (Malvaceae) due to their small, orange, über-staminate flowers. Immediately I spotted the familiar thorn-like shape of treehoppers in the tribe Membracini, probably a species of Enchenopa or related genus. I had been hoping to see more of these after photographing another species further south in Buenos Aires last year, but I hadn’t seen a single treehopper during the entire week. Fortunately I had my 65mm lens already on the camera, so I quickly snapped a few shots and collected a couple of specimens. Just as quickly as I had done that, I heard somebody yelling to me from the road above that people were getting back into their cars ahead. These few shots and specimens would have to do. (And, disappointingly, after spending the next hour creeping towards the bridge there wasn’t even a wreck to look at!)

As I did with those previous photos, I sent these to Andy Hamilton (Canadian National Collection, Ottawa), who forwarded them on to Dr. Albino Sakakibara (Universidad Federal de Parana, Brazil) and then reported back to me that:

My Brazilian colleagues…have been able to identify your “beautiful photos” as representing Enchenopa gracilis, a species that has been illustrated only once (in 1904), and certainly not by a photograph!

Another individual, this one with no trace of green colorationi and less distinctly marked wings.

The illustration referenced by Andy comes from Kellogg (1905—p. 169, fig. 239), and as he notes at BugGuide the problem with old illustrations is that many of them are either inaccurate or use obsolete names. Enchenopa gracilis does not occur in North America, thus the drawing in Kellogg (1905) probably does not actually represent this species. Nevertheless, a recent dissertation on the insect fauna associated with pigeon pea in Brazil (Azevedo 2006) shows several photographs of adults that agree nicely with these photos. Enchenopa gracilis actually seems to be a bit of a pest on that crop, and it has also been reported in association with a variety of other plants across several different families (Lopes 1995, Alves de Albuquerque et al. 2002). Interestingly, I could not find any species of the family Malvaceae recorded as a host for E. gracilis.

REFERENCES:

Azevedo, R. L. 2006. Entomofauna associada ao feijão guandu [Canjanus cajan (L.) Millspaugh] no recôncavo baiano. Ph.D. dissertation, Centro de Ciências Agrarias e Ambientais, Universidade Federal da Bahia, Cruz das Almas, 54 pp.

Alves de Albuquerque, F., F. C. Pattaro, L. M. Borges, R. S. Lima & A. V. Zabini. 2002. Insetos associados à cultura da aceroleira (Malpighia glabra L.) na região de Maringá, Estado do Paraná. Maringá 24(5):1245-1249.

Kellogg, V. L. 1905. American Insects. Henry Holt & Co., New York, 674 pp.

Lopes, B. C. 1995. Treehoppers (Homoptera, Membracidae) in southeastern Brazil: use of host plants. Revista Brasileira de Zoologia 1213:595-608.

Copyright © Ted C. MacRae 2012

“Cochinilla australiana” in Argentina

Icerya purchasi (''cochinilla australiana'') on citrus twig | western Buenos Aires Province, Argentina

After traveling through the northern provinces during late March and early April, I returned to my home base in western Buenos Aires Province for the last two weeks of my stay in Argentina. As soon as I could, I returned to the small grove of planted citrus trees on the station grounds where I had found a rather large, beautifully cryptic fulgorid nymph (see “Seeing the unseen“). Lois O’Brien had mentioned in her response to my query about the identity of the nymph that some species of Fulgoridae tend to live on the same tree for years and years—if I could go back to the tree on which I found the nymph perhaps I could find the adult. Sadly, no adults or additional nymphs were found, either on the original tree or any in its vicinity. What I did find, however, was this strange, cocoon-like structure on one of the branches of the tree. I had no idea what it was, having never seen anything quite like it, but I figured something—pupa, eggs, parasitoid, etc.—must be inside. I cut the piece of branch with the structure and tucked it inside a vial for later.

Egg case opened to reveal eggs and newly hatched nymphs

A little bit of searching online would have quickly told me what I was dealing with, but for some reason I felt the need to go ahead and start dissecting to see what was inside. It became obvious I was dealing with an egg mass when I peeled back the outer layers to reveal the cluster of red eggs inside, and very quickly I noticed that a few of the eggs had already hatched. The red nymphs had a decidedly “homopterous” look to them, and not much effort was required to figure out that I was looking at my very first “cottony cushion scale” insect.

Closer view of eggs - newly hatched nymph can be seen at bottom.

Icerya purchasi (Hemiptera: Monophlebidae) originally hails from Australia, but its preference for citrus and the realities of global commerce have resulted in its inevitable spread across the globe wherever citrus is grown (maybe I can be forgiven for having never before seen such a widespread insect—living most of my life in Missouri and northern California, I’ve not had much opportunity to visit citrus groves). The English common name clearly references the appearance the adult female, recognizable by the white, fluted egg sac shown here, while in Argentina it is called ”cochinilla australiana”—literally meaning “Australian scale insect.”

Newly hatched nymphs are bright red with dark antennae and thin brown legs.

As I dissected the egg sac, a few of the newly hatched nymphs crawled out of the sac an onto the branch. Nymphs of this stage are referred to as “crawlers” because they are the dispersal stage. It’s a good name for these tiny little bugs, as the several that I tried to photograph never stopped moving. With the lens fully extended to 5X, it was difficult enough to just find them in the viewfinder, much less compose and focus with all the movement. It became a numbers game and test of patience—how many shots could I get fired off in the amount of time that I was willing to persist? Shown here are the few shots that I was the least displeased with.

First instar nymphs are the primary dispersal stage.

Crawlers disperse not only by crawling, but also by wind. One can imagine that such tiny insects could easily be picked up by the wind and carried long distances. However, I couldn’t help but notice the very long setae on the body and outer antennal segments (visible to greater or lesser degree in these photos) and think that perhaps they have some function in aiding wind dispersal. At the very least, aerial dispersal must be as important as crawling (if not more so) for colonization by this species—only adult males have wings (but they are rare), while egg-laying females (actually hermaphrodites) are completely sessile.

Do the long setae on the body and antennae of the nymph aid in wind dispersal?

The adult female and egg case may have confused me initially, but a ton of readers had no problem figuring out what it was. A record 24 people participated in this challenge, with all but five correctly guessing the species. Winning this challenge came down to bonus points for speed and uniqueness of additional information, and Christopher Taylor did this best to earn 17 pts and the win. Three others—Brady Richards, Mr. Phidippus and bicyclebug—each finished just 1 pt back of the win, but Sam Heads’ 15 pts keeps the overall lead in his possession. BitB Challenge Session #6 is young, but already a lot of people have a lot of points in the bank. It will be interesting to see how this session develops.

Copyright © Ted C. MacRae 2012

ID Challenge #17

 

Welcome to ID Challenge #17. As in recent challenges, points are on tap not only for naming the organism (in this case, order, family, genus and species) but also for explaining the visible structures. Standard challenge rules apply, including moderated comments, tie-breaker points for first correct answers, and possible bonus pts for other information I deem to be relevant.

 

Copyright © Ted C. MacRae 2012

Inaugural “One-Shot Wednesday”

On many occasions I have considered making my own contributions to the “Wordless Wednesday” meme. Unfortunately, I find it impossible to post photos of insects and not be allowed to say anything about them. I suppose I could follow Dragonfly Woman‘s “Well-Nigh Wordless Wednesday” example, but that seems like horning in on somebody’s trademark. At last it finally occurred to me a meme that I could use for Wednesday’s that gets around these issues—”One-Shot Wednesday”! Ever photograph an insect and only get off a single shot? Not just one keeper from a series of photos, but only one single photo of the insect, like it or lump it! That’s what I’m talking about here. The subtext, of course, is that there was only that one chance to get everything right—exposure, focus, composition, lighting, etc. Obviously, it’s not my plan to show crappy photos as part of this meme, but rather that occasional instance where I only got off a single shot, and for the most part everything worked pretty well to produce a decent photograph. I would, of course, be more than happy to see this meme take off and spread throughout the insect blogging community, but if it doesn’t and it remains a BitB exclusive then that’s fine also.

Leptoglossus sp. | nr. Corrientes, Argentina

Here is contribution #1 in the meme: a leaf-footed bug (family Coreidae) feeding on flowers of Solidago chilensis  that I photographed a couple of weeks ago near Corrientes, Argentina. According to coreid-specialist Harry Brailovsky (Universidad Nacional Autónoma de México), the expanded hind tibiae place it in the large, mostly New World genus Leptoglossus. Which one, however, is a good question—according to Coreoidea Species File Online, ten species in the genus have been recorded in Argentina, but browsing through available images didn’t immediately turn up a good match for the individual shown in this photo.

I’ve often wondered about the purpose of the leaf-like expansions of the hind tibiae of coreids—which reach truly gargantuan proportions in some tropical species—and their adaptive significance. One can imagine they might serve as a “false target” for potential avian predators, and supporting this idea is the fact that the hind legs seem to break off rather easily when handled. It’s not rare to find individuals in the field missing one or even both hind legs.

Copyright © Ted C. MacRae 2012