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

I fear no weevil…

Megabaris quadriguttatus (Klug, 1829) | Corrientes Province, Argentina

…especially when they are as colorful as these! I found this mating pair ~60 km south of Corrientes, Argentina feeding on flowers of what I presume to be the goldenrod species Solidago chilensis (family Asteraceae). Here, as in North America, goldenrod blooms in profusion along the roadsides during late summer and fall wherever moisture is to be found, and also as in North America goldenrod here is an insect magnet. During my week exploring Corrientes and Chaco Provinces, I learned to stop whenever I spotted a stand of the distinctive yellow blossoms. I found several stands and was treated to a variety of beetles, flies, and other insects that I’ll show over the coming days, with these being among the most striking that I found.

Weevils themselves may not be anything to be afraid of; however, their taxonomy is downright terrifying (and this coming from a beetle man!). With more than 40,000 described species worldwide (and who knows how many still awaiting description), the family Curculionidae (“true” weevils) may be the largest in the animal kingdom. I don’t know why, given the distinctive and striking coloration of these individuals, but I punted early and asked my friend Henry Hespenheide (a buprestid man, but knows a thing or two about weevils) if he knew what these were. Henry must have also been scared, because he went straight to the top and forwarded the photos to weevil heavy-hitters Charles O’Brien and Jens Prena, both of whom quickly replied back with an ID of Megadaris quadriguttatus (Klug, 1829). The state of weevil bionomics seems to be as incomplete as their taxonomy, as I was unable to find even the most basic information about the distribution and biology of this species (keep in mind I’m in Argentina right now with no access to libraries). As far as I can tell this is a strictly Neotropical genus.

Of course, had I checked Curculionidae de Argentina I might have noticed the photo of this species right there on the front page. Fear does strange things to one’s confidence.

Copyright © Ted C. MacRae 2012

The backwards firefly

Aspisoma sp. | Buenos Aires Province, Argentina

The beetle in these photos was another “gift” from my colleagues in Fontezuela, Argentina—brought to me shortly after I found the first gift on my desk during my first week at the station. This is obviously a firefly, but I also recognized it as the same species as (or very close to) one I had photographed in a soybean field during last year’s March visit. I only got off one shot of the one in the soybean field before it took flight, so here are some better views of the species—enhanced by the cleanliness inside the pearly white confines of a styrofoam cooler.

A little closer...

My attempts to identify the species last year were fruitless (though admittedly cursory). This year I tried a different tact—I went to the website Lampyridae de Argentina (which is really just a list of species based on Blackwelder’s Neotropical beetles checklist) and did a Google image search on each genus in the list (combined with the term “Lampyridae”) until I encountered something that looked pretty close in the genus Aspisoma (tribe Photinini) in the Lampyridae photo gallery at PyBio.org (Paraguay Biodiversidad). The page contains excellent dorsal habitat photographs of a number of species in the genus; however, unfortunately the majority of them are labeled simply as Aspisoma sp. (it should not be surprising that the state of lampyrid taxonomy in South America is still far from complete). The individual shown here is a dead ringer for Aspisoma sp. #8, but spp. #51, 52, and 53 cannot be discounted. I sent the photos to cantharoid beetle expert Santiago Zaragosa Caballero, who confirmed the species appeared to be a member of the genus Aspisoma but admitted to not knowing the South American fauna well enough to offer a species ID. Nevertheless, a genus ID is better than nothing, and my thanks to Santiago for his confirmatory ID.

...and finally, the requisite ''face'' shot.

It’s no secret that I love face shots! The above photo, however, was the best I could do for this species due to its highly explanate (flanged) pronotal hood and the typical firefly habit of hunkering down and using their flange to protect their softer underparts when feeling threatened. I call this the “backwards” firefly because everything about it seems opposite to my concept of fireflies in eastern North America—yellow with black markings instead of black with yellow markings and active during the day instead of at night, which I most easily ascribe to its occurrence opposite to the Northern Hemisphere! (wink)

Copyright © Ted C. MacRae 2012

A tortoise beetle gift

Chelymorpha varians | northwestern Buenos Aires Province, Argentina

A few days after returning from travel through northern Argentina, I found a jar on my desk with this beetle in it. One of my colleagues has seen it in the field while I was away and figured I would be interested in seeing it. Although I’m half-a-world away from home, I immediately thought of our North American species Chelymorpha cassidea when I saw it. Armed with this hunch, I typed “Chelymorpha Argentina” into Google, and the first result that came up was a paper by Hamity & Neder de Román (2008) about the species Chelymorpha varians in Argentina and its potential as a biocontrol agent for the widespread weed Convolvulus arvensis. Included in the paper was a plate showing variability of coloration and maculation in the adults, and my individual was a dead ringer for the species. Still, getting a species ID on the very first hit of the very first search attempt just seemed too easy, so I consulted the wonderfully comprehensive Cassidinae of the world – an interactive manual. This site, too, contained multiple images of Chelymorpha varians showing an extraordinary range of variability in color (from yellow to red) and degree of maculation (from immaculate to heavily maculated). A quick perusal of other species indicated as similar or also occurring in Argentina turned up nothing nearly as similar and convinced me that I had, indeed, arrived at a correct ID.

As the name suggests, markings are highly variable in shape and degree of development.

As indicated in the above cited paper, and like our own C. cassidea, species in the genus Chelymorpha are associated almost exclusively with plants in the genus Convolvulus. I would have preferred to photograph the beetle on foliage of this plant, but not knowing precisely where I might find it I decided to do white box instead. I got some printer paper and was looking for a cardboard box to line the inside with it when I spotted a styrofoam cooler of just the right size.

The scientific name translates literally to ''variable turtle-body''

These are okay white box photos, but I’ve decided if I want to do white box right I need to get a larger flash unit that is a little easier to work with off the camera. Right now I have only the small twin-flash heads from my MT-24EX—their small size makes them difficult to manipulate off the camera, and leaving them attached to their bracket limits the directions in which they can be oriented relative to the subject. As a result, I had to use more heavy-handed post-processing in these photos than I normally like to do in order to get the levels right. Hmm, I have a birthday coming up in about a month…

REFERENCE:

Hamity, V. C. & L. E. Neder de Román. 2008. Aspectos bioecológicos de Chelymorpha varians Blanchard (Coleoptera: Chrysomelidae, Cassidinae) defoliador de convolvuláceas. Idesia 26(2):69–73.

Copyright © Ted C. MacRae 2012

Retrachydes thoracicus – times four!

Disclaimer—these are not great photos!

A few days ago I posted this little quip as my status on Facebook: “Cool! Found a Retrachydes thoracicus thoracicus on the sidewalk outside my hotel!” I chuckled a little as I posted it, knowing that only a select few who read it would know what the heck I was talking about (of course, a right click to select “Search with Google” reveals the answer instantly). Of course, it is a species of longhorned beetle (family Cerambycidae) that apparently is found commonly in South America. I wanted to take some photographs of the beetle to show those who didn’t do the Google search just what it looked like. Unfortunately, the beetle was already somewhat moribund when I found it, and no matter how much I coaxed and prodded it on the stick I placed it on, it just looked… well, dumb. Legs out of position, antennae hanging limply, and the beetle itself laying prostrate on the branch, as if it barely had the strength to hang on (which actually was the case). Shame—it sure is an attractive species, with its densely pubescent and transversely gibbous pronotum (obviously the source of its name) and striking orange-banded antennae. C’est la vie!

Lately I’ve been trying to get a better handle on choosing backgrounds when I photograph insects, no longer content with the often busy and distracting backgrounds that show up in photographs taken completely in situ. It’s often a simple matter to hold the object on which the insect is sitting in front of something that gives the desired background effect, and having this perfectly calm yet strikingly attractive beetle to work with seemed to invite experimentation. I’m also trying to get a better feel for how to use higher ISO settings to make it easier to get these various “non-black” backgrounds while still using flash to get acceptable depth of field with the subject itself. Below are four of the better shots that came out of the session (yes—sadly, these are the “better” ones). I’m loathe to go below 1/160 sec exposure because of motion blur and would like to keep aperture settings quite small, so fairly high ISO settings are required to get the background effects I’m looking for. I think I’ve learned that ISO 1000 is about as high as I can go before the background gets unacceptably noisy—at small sizes the photos look fine, but open them up larger size and you’ll see what I mean. Anyway, ignoring the composition and noise issues, which background do you like best?

ISO 1000, 1/160 sec, f/14 - cloudy sky background

ISO 1600, 1/160 sec, f/14 - pavement background (close)

ISO 1600, 1/160 sec, f/14 - pavement background (more distant)

ISO 1600, 1/160 sec, f/14 - pavement background (foliage)

Copyright © Ted C. MacRae 2012

The most common beetle in Argentina

Astylus atromaculatus | Buenos Aires Province, Argentina

I don’t know if this is truly the case, but Astylus atromaculatus (family Melyridae) is one of only a few beetles in the country that actually has two Spanish common names—”astylus moteado” and “siete de oro” (meaning “spotted astylus” and “seven of gold”, both names referring to black splotches on the elytra). It is also the only beetle that I’ve seen everywhere I’ve been in the country—north and south, soybean fields and cornfields, countryside and city. I have yet to visit a soybean field where I don’t see them, perhaps nibbling on a leaf here and there but mostly just mating, and they can be downright overwhelming in cornfields (see this post with photos of the adults dripping from corn tassels, literally!). For all their ubiquity, however, their economic impact seems more nuisance than substantive. Corn breeders complain about interference during tasseling, and larval feeding on seeds during or just after germination seems to be on the rise due to increased use of conservation tillage, but overall this species seems to be more bark than bite.

Copyright © Ted C. MacRae 2012

Eriopis connexa on soybean in Argentina

Eriopis connexa adult on soybean | Buenos Aires Province, Argentina

Congratulations to those of you who correctly guessed the identity of the “subject” in ID Challenge #16 as the ladybird beetle Eriopis connexa (family Coccinellidae). This is one of the most common ladybird beetles in Argentina, and during the past few weeks I have seen large numbers of these beetles in the soybean fields that I have been visiting. Coccinellids in Argentina are among the easier the groups to identify to species thanks to the excellent website Coccinellidae of Argentina. Identifying the “meal,” however, proved to be a little more difficult. Most people guessed aphids, a natural choice, but soybean aphids have not yet made it to the soybean fields of South America (thankfully!), so the victims of these predaceous beetles must be something else. There was a clue in the challenge photo that at least one person picked up on (but didn’t make the connection) in the form of small black globs stuck to the hairs of the plant on which the beetle was sitting. These are actually the fecal deposits of the bean thrips, Caliothrips phaseoli (order Thysanoptera, family Thripidae) (which I covered a year ago in A thrips is a thrips…), which for the past two seasons now has built up large populations on soybeans in Argentina. In fact, an adult bean thrips (yes, “thrips” is the correct singular form) can be seen in the above photo (which I did not notice while I was taking the photo). I’ve not yet witnessed these beetles actually feeding on a thrips, but the large numbers of thrips and beetles and near absence of any other suitable prey item makes the association almost a given.

Eriopis connexa larva on soybean | Buenos Aires Province, Argentina

Not only are the adult beetles numerous on the plants, but eggs and larvae as well. Larvae are every bit as brightly colored as the adults, with a color scheme that leaves little doubt regarding their association. In the case of this larva, I watched it roam back and forth across the soybean leaf, pausing momentarily and apparently eating something—thrips eggs I presume.

Congratulations to Mr. Phidippus and Dennis Haines, who tie for the Challenge win with 14 points each, while Gustavo and Dave tie for the final podium spot. Mr. Phidippus, however, easily takes the overall win in BitB Challenge Session #5 with a whopping total of 57 points. Mr. Phidippus—contact me for your loot! Dennis Haines and Tim Eisele take 2nd and 3rd overall honors, and full standings for BitB Challenge Session #5 are shown below.

Commentor	IDC#14	SSC#10	IDC#15	Bonus	SSC#11	Bonus	IDC#16	Total
Mr. Phidippus	11	11	9		12		14	57
Dennis Haines	9	4	2		10	1	14	40
Tim Eisele	8	6	2		13		6	35
Roy	5	6	7		10			28
Mike Baker	7		9				10	26
Dorian Patkus			9		11	4		24
David Winter	3		9				10	22
Gustavo							12	12
HBG Dave							12	12
Marlin	12							12
FlaPack	10							10
Laurie Knight	2				8			10
Doug Yanega					9			9
Brady Richards				4		3		7
John Oliver		6						6
George Sims	2	2	2					6
Richard Waldrep			6					6
Arpad Hervanek	4							4
Roxane Magnus	4							4
dragonflywoman					4			4
Wayne K					4			4
itsybitsybeetle					4			4
fatcatfromvox	2							2
Emily Gooch	1							1
Sean Whipple			1					1
Jon Q							1	1

 

Copyright © Ted C. MacRae 2012