Coleoptera

Beetles. The largest order of animals with more than 300,000 species in about 2000 genera.

Giving me the weevil eye!

/ Ted C. MacRae / 7 Comments

The order Coleoptera (beetles) is, of course, the largest single group of animals on earth, and by most accounts the Curculionidae (weevils) and their close relatives are the largest family-level group within the order. At 60,000 species and counting, weevils account for approximately one out of every 20 described life forms, and as a result their diversity of forms, colors and life histories are as staggering as their numbers. Among the small slice of the group that I have seen, Megabaris quadriguttatus is without question the most colorful, but species in the related genus Eurhinus (both genera belong to the curculionid subfamily Bardinae, which I point out here for reasons discussed below) must rank as among the shiniest of all weevils. Twenty-three species, all colored brilliant metallic green, blue, purple or red, are known from this exclusively Neotropical genus (Vaurie 1982), one of which has also recently established in southern Florida (Ulmer et al. 2007). The individual featured in this post was seen April 2012 in northern Argentina near La Escondida (Chaco Province) and compares well with Eurhinus adonis (ID courtesy Charles O’Brien, Green Valley, AZ). Vaurie (1982) records that species from southern Brazil, Bolivia, Paraguay and Argentina (although only from Missiones Province in the latter) and says that nothing is known of its biology.

Giving me the weevil eye!

Eurhinus cf. adonis on Solidago chilensis | Chaco Province, Argentina

This is certainly among the most challenging insects that I’ve ever photographed. Overblown specular highlights are a constant challenge in flash macrophotography of bright, shiny, metallic beetles, and yellow flowers are prone to blown highlights as well. Add on top of that my desire for a blue sky rather than the typical black background and the usual difficulties of hand-held, field photography of an actively moving subject, and you’ve got a quadruple challenge. Adequate diffusion of the flash is critical, and although the diffusers I was using at the time weren’t perfect, they were enough in combination with intentional underexposure of the photograph to further minimize the chance of blown highlights (underexposed photographs can be relatively easily “fixed” during post-processing, as all of the information is still there, while overexposed photographs can rarely be fixed because the information is gone). Bumping up the ISO (in this case 400) also helps—higher sensitivity to light by the sensor not only allows light from the sky to register and create a blue background, but also further reduces flash duration and the risk of blown highlights. No amount of camera settings, however, can address the final challenge—getting the subject well composed and in focus within the frame. For that, the three “P”s (patience, practice, and persistence) are the only advice I can offer.

Eurhinus cf. adonis on Solidago chilensis flowers | Chaco Province, Argentina.

What’s in a name? That which we call a Eurhinus by any other name would be as shiny!

This genus of weevils was involved in one of the more interesting nomenclatural problems that I’ve encountered. The genus was originally given the name Eurhin by Illiger in 1807, but Schönherr in 1824 changed it to Eurhinus—believing (incorrectly) that Eurhin was not a properly formed name. Unfortunately, the name Eurhinus had already been used by Kirby in 1819 for a different genus of weevils in the subfamily Apioninae. The rules of zoological nomenclature, of course, prohibit the same name being used for two different genera, and several attempts were made during the following years to provide a replacement name for Schönherr’s Eurhinus. None gained acceptance, however, and eventually Schönherr in 1833—still considering justified his correction of Eurhin to Eurhinus—proposed the name Eurhynchus for Kirby’s Eurhinus. Remarkably, the name Eurhynchus also had been used previously (for a genus of birds). Nevertheless, the change gained acceptance, and both of Schönherr’s names remained in use for the next century and a half—Eurhinus in the subfamily Baridinae and Eurhynchus in the subfamily Apioninae, with both credited to Schönherr. Strict application of the rules of nomenclature would require that the name Eurhinus be transferred back to the apionine genus and credited to Kirby and the name Eurhin resurrected for the baridine genus and credited to Illiger. However, as pointed out by Zimmerman & Thompson (1983) this would not only destroy more than a century’s worth of nomenclatural stability but also complicate the formation of family-group names such as tribes—since the two original names each have the same root (Eurhin-), tribal names based on them would be identical (Eurhinini). To resolve these issues, a formal application was submitted to the International Commission of Zoological Nomenclature (ICZN) to preserve  Schönherr’s long accepted usage of Eurhinus and Eurhynchus. To do this, the ICZN would not only have to declare Schönherr’s correction of Eurhin to Eurhinus justified, but also suppress the original use of the name Eurhynchus (as a genus of birds) in order to allow Schönherr’s subsequent use for the apionine genus to stand. Fortunately, suppressing the first use of Eurhynchus had no impact on stability, since an older name was already in use for the genus of birds and the younger name had not been used since its original description. The authors of the application also noted the support of several contemporary weevil specialists (including Charles O’Brien) and that Patricia Vaurie, in her revision of the genus one year earlier (Vaurie 1982), had used the original name Eurhin with reluctance on the then-correct advice of her contemporaries. It was a classic case of priority versus stability, and while the ICZN typically is rather conservative in favoring priority, they were clearly swayed in this case by the interests of stability and impact on formation of family-group names.

REFERENCES:

Ulmer, B. J., R. E. Duncan, J. Prena & J. E. Peña. 2007. A weevil, Eurhinus magnificus Gyllenhal (Insecta: Coleoptera: Curculionidae). University of Florida, IFAS Publication #EENY-417/IN751, 6 pp.

Vaurie, P. 1982. Revision of Neotropical Eurhin (Coleoptera, Curculionidae, Baridinae). American Museum Novitates 2753:1–44.

Zimmerman, E.C. & R. T. Thompson. 1983. On family group names based upon Eurhin, Eurhinus and Eurhynchus (Coleoptera). Bulletin of Zoological Nomenclature 40:45–52.

Copyright © Ted C. MacRae 2013

Group mimicry in Cerambycidae… and more

/ Ted C. MacRae / 2 Comments

During last year’s extended visit to Argentina, I had the chance to spend the early part of April in the northern province of Chaco. Though much of this hot, arid plain has been converted to agriculture, remnants of thorn forest remain along fence rows and in small patches of Chaco Forest. Despite the decidedly tropical latitude of the region, however, the profuse bloom of Chilean goldenrod, Solidago chilensis, along these fence rows during the Argentine autumn is reminiscent of crisp fall days here in the eastern U.S., and like the goldenrod here the ubiquitous stands of yellow blossoms stretching across the Chaco Plain are equally attractive to a multitude of insects. Among those insects are the Cerambycidae, or longhorned beetles, and while the eastern U.S. cerambycid fauna of goldenrod boasts only a few (albeit spectacular) species in the genus Megacyllene, the Argentine cerambycid fauna that I found on these flowers included at least three species in various genera belonging to two different tribes.

Rhopalophora collaris (Germar 1824) | Chaco Province, Argentina

Rhopalophora collaris (Germar 1824) | Chaco Province, Argentina

Two of the species I saw are shown here, and their similarity of appearance is no coincidence, as both belong to the tribe Rhopalophorini (coming from the Greek words rhopalon = club and phero = to bear, in reference to the distinctly clavate, or club-shaped, legs exhibited by nearly all members of the tribe). In fact, a great many species in this tribe exhibit the same general facies—slender in form and black in coloration with the head and/or pronotum red to some degree. Since all of these species are diurnal (active during the day) and frequently found on flowers, one can assume that the members of this tribe represent an example of what Linsley (1959) called ‘group mimicry.’ In this simple form of Batesian mimicry (harmless mimic with protected model), a group of related species within a genus or even a tribe have a general but nonspecific resemblance to those of some other group of insects—in this case presumably small, flower-visiting wasps. Although the tribe is largely Neotropical, the nominate genus Rhopalophora does extend northward with one eastern U.S. representative, R. longipes. Among the numerous species occurring in South America, the individuals I saw in Argentina can be placed as R. collaris due to the relative lengths of their antennal segments and uniquely shaped pronotum (Napp 2009).

Cosmisoma brullei (Mulsant 1863) | Chaco Province, Argentina

Cosmisoma brullei (Mulsant 1863) | Chaco Province, Argentina

The second species could easily be mistaken for another species of Rhopalophora were it not for the distinct tufts of hair surrounding the middle of the antennae. These tufts immediately identify the beetle as a member of the large, strictly Neotropical genus Cosmisoma (derived from the Greek words kosmos = ornament and soma = body, a direct reference to the tufts adorning the antennae of all members of this genus). Three species of the largely Brazilian genus are known from Argentina, with the black and red coloration of this individual easily identifying it as C. brullei (Bezark 2o13). In the years since this genus was described, additional related genera have been described that bear remarkably similar tufts of hair not on the antennae, but on the elongated hind legs. The great, 19th century naturalist Henry Walter Bates “tried in vain to discover the use of these curious brush-like decorations” (Bates 1863), and nearly a century later Linsley (1959) conceded that their function still remained unknown. Antennal tufts are actually quite common in Cerambycidae, especially in Australia, and while experimental evidence continues (to my knowledge) to be completely lacking, Belt (2004) records observing “Coremia hirtipes” (a synonym of C. plumipes) flourishing its leg tufts in the air (presumably in a manner similar to waving of antennae) and, thus, giving the impression of two black flies hovering above the branch on which the beetle was sitting. This seems also to suggest a function in defense, with the tufts perhaps serving as a distraction to potential predators in much the same way that many butterflies have bright spots near the tail to draw the predator’s attention away from the head.

REFERENCES:

Bates, H. W. 1863. The Naturalist on the River Amazons. Murray, London, 2 vols.

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

Bezark, L. G. 2009. A Photographic Catalogue of the Cerambycidae of the World. Available at http://plant.cdfa.ca.gov/byciddb/

Linsley, E. G. 1959. Ecology of Cerambycidae. Annual Review of Entomology 4:99–138.

Napp, D. S. 2009. Revisão das espécies sul-americanas de Rhopalophora (Coleoptera: Cerambycidae). Zoologia (Curitiba) 26(2):343–356.

Copyright © Ted C. MacRae 2013

And the results are in…

/ Ted C. MacRae / 30 Comments

I recently entered my first photo contest, a local competition sponsored by the Webster Groves Nature Study Society (of which I have been a member for ~30 years), and although the competition was limited to its few hundred members there were some serious cash prizes on offer. Being a noob at photo contests and a still relative newcomer to photography in general, I wasn’t sure what to expect. I thought my photos might be good enough to compete, but I also knew I would be going up against some long-time and very skilled nature photographers. The basic rules were a maximum of two submissions in no more than three of the following categories:

  • Botany
  • Entomology
  • Ornithology
  • Landscapes/habitats

Since I’ve only photographed two birds ever, I decided to submit entries to each of the other three categories. It was an interesting competition—the judges (each category had a panel of three consisting of a WNGSS board member, a natural history expert, and a photography expert) had a chance to see all of the photographs prior to the event (held last night) and select the top ten from each category, but the rest of the judging was done live at the event. Eventually, from each category a 1st place, 2nd place, and 3rd place photo was selected. The 12 winning photographs were then displayed in a continuous loop, and everybody attending the event was allowed to vote for one grand prize winner. The grand prize winner had to receive more than 50% of the vote, so a few runoff rounds were required to decide the final winner.

How did it go for me? I had a pretty good night, with three winning photographs:

Entomology—3rd place

Cicindela repanda (Bronze Tiger Beetle) | St. Louis Co., Missouri

Cicindela repanda (Bronze Tiger Beetle) | St. Louis Co., Missouri

Botany—2nd place

Hamammelis vernalis (Ozark witch hazel) | Iron Co., Missouri

Hamammelis vernalis (Ozark witch hazel) | Iron Co., Missouri

Entomology—1st place

Arctosa littoralis (beach wolf spider) | Lewis Co., Missouri

It was a thrill for me to learn that, out of the six photographs I submitted (and I really didn’t think my two landscape submissions were competitive to begin with), three were among the 12 final prize winners. That also made them eligible for the grand prize, but in this case I didn’t really expect the larger membership (which has a lot of birders) would really take to my closeup insect photographs. To my surprise, the first round of voting produced four finalists—two of which were my insect photos! The first runoff vote eliminated one photo—but not either of mine, and the second runoff eliminated one more photo—but again neither of mine. I had won the grand prize without yet knowing which photo would be the winner! In the end, the tiger beetle took the top prize. Personally, I was happy about that, because even though the photo took only 3rd place in the entomology competition, I thought it was the stronger of the two photos based on composition, the time and effort it took to work the beetle to finally “get the shot” (not that the wolf spider photo didn’t also take a lot of effort to get that close), and the natural history behavior that it captured (stilting and sun-facing for thermoregulation). I know blog commenting is becoming passé, but if you have any particular thoughts about these photos, good or bad, I would love to hear from you.

Overall I would have to say that, winner or not, participating in a photo competition was an extraordinary learning opportunity for me as I try to hone my craft. Listening to the comments of the judges in all of the categories, both on the natural history and the technical aspects of the photographs, gave me a lot of insight into how I might further improve my technique and take photographs that can be appreciated on both technical and artistic grounds. More importantly, the cash was nice, but the motivation to keep trying that I got out of the experience was priceless!

Copyright © Ted C. MacRae 2013

Ceti Eel offspring?

/ Ted C. MacRae / 5 Comments
Nicrophila americana

Nicrophila americana (American carrion beetle) larva | Sam A. Baker State Park, Wayne Co., Missouri.

If this creature was a tad bit slimier, you might think it had just been plucked from underneath the armor of an adult Ceti Eel and was looking to slip inside the ear of Chekov or some other human to wrap itself around the unsuspecting victim’s cerebral cortex. In reality, this creature lives not on Ceti Alpha V., but right here on earth, and while it’s natural history may not include making human hosts “extremely susceptible to suggestion“, it does include an appetite for dead flesh and the maggots that try to compete for it. Say hello to the larva of Nicrophila americana (American carrion beetle), a member of the family Silphidae (carrion and burying beetles) (not to be confused with the endangered Nicrophorus americanus, or American burying beetle). Like most beetles, the larvae can be difficult to recognize as such due to its very different form compared to the adult. However, the one-segmented tarsi, distinct head, presence of chewing mouthparts, and presence of spiracles along the sides of the body give the clues to its identity.

Necrophila americana

While not the offspring of a Ceti Eel, its habits are almost as… er, disgusting!

The genus name (literally meaning “attracted to corpses“) is a perfect descriptor of this beetle’s natural history. Adults are attracted to animal carcasses, where they lay their eggs and prey on maggots (fly larvae) as they hatch to give a competitive advantage to their own larvae once they hatch. The larvae also will eat maggots and other larvae within the carcass, along with the carcass itself. This larva had completed its development and was searching the ground for a suitable spot to dig a burrow for pupation and eventual emergence as an adult.

Copyright © Ted C. MacRae

The “little soybean weevil”

/ Ted C. MacRae / 6 Comments

Lepidopteran caterpillars are without question the most important pests affecting soybean in South America, while stink bugs run a close second in terms of economic impact and as the targets of insecticide applications. There are, however, a number of weevil species (order Coleoptera, family Curculionidae) whose incidence has increased during the past decade or so as the area planted to soybean continues its decade’s long expansion on the continent. The most important of these is Sternechus subsignatus, a  relatively large (and rather attractive black-and-yellow) species that was first detected in southern Brazil in the 1970s. It has since spread to northern Brazil and in recent years has also begun affecting soybean in Salta and Tucumán Provinces of northern Argentina (sometimes considered a distinct species, S. pinguis). Known locally as “picudo grande” (big weevil), adults clip the petiole of leaves and girdle the stems, leading to stand loss. One adult is capable of killing multiple plants, so that even light infestations can result in severe damage.

IMG_2439_enh_1080x720

Promecops carinicollis | Tucumán Province, Argentina

I’ve not yet seen “big weevils” for myself, but there are at least two other species that are showing up in soybean fields, particularly in Salta and Tucumán Provinces. During my recent visit to Argentina I happened upon a soybean field in northern Tucumán infested with one of them, Promecops carinicollis, a few photos of which I show here. This species is much smaller than S. subsignatus and is, thus, called “picudo chico” (little weevil)—certainly an appropriate name for the 3- to 4-mm long adults. While the integument is black, the body is densely covered with flat scales that form irregular white blotches on the elytra and otherwise give the beetle a mottled-brown appearance.

IMG_2436_enh_1080x720

Damage consists of adult feeding around the leaflet margins, giving them a scalloped appearance.

Like S. subsignatus, it is the adults that cause damage to the plants, although instead of the stems and petioles their feeding seems to be confined to the margins of the leaflets. This gives the leaflets a “scalloped edge” appearance that is quite distinctive and unlike the leaf damage caused by other leaf-feeding insects of soybean. The feeding causes a general reduction of the leaf surface area of the plant, which reduces the plant’s capacity to photosynthesize. However, as soybean has a rather high capacity to compensate for foliage loss by growing new foliage, especially during the earlier vegetative stages of growth, it would take rather high pressure by these weevils to cause enough damage to result in yield loss. It may be one of those soybean pests for which insecticide applications are made much more often than is warranted. The most important impact of this insect probably occurs just after seedling emergence, during which time feeding on the cotyledons and first leaves can weaken seedlings enough to cause stand loss.

Promecops carinicollis | Tucumán Province, Argentina

Beginning the process of making more Promecops carinicollis.

Copyright © Ted C. MacRae 2013

Baffling beetles

/ Ted C. MacRae / 12 Comments

Even though I pride myself as a fairly competent coleopterist, I occasionally run into beetles that—despite my best efforts—I just cannot identify them beyond the family level. I don’t feel too bad about that, as the group’s 350,000 to 400,000 described species represent more than a third of all described life forms! Still, with the amount of information now available online combined with traditional print literature, it’s frustrating when I photograph species that seem quite distinctive but fail to show up in any search result. Here are a couple of South American beetles that I’ve pondered over for a year or more now. If you have any thoughts on their identity I would appreciate hearing from you.

Tenebrionidae? | Campinas, São Paulo, Brazil.

Tenebrionidae? | Campinas, São Paulo, Brazil.

This first beetle was encountered January 2011 on the trunk of a tree in the city of Campinas, southeastern Brazil (São Paulo State). I only got this one shot of it before it dropped and disappeared, and except for the bright green color of the head and pronotum it reminds me of some of the long-jointed beetles—formerly the family Lagriidae but now a subfamily of Tenebrionidae (darkling beetles).

Elateridae | Rt 16 nr. Rio Nego, Chaco Province, Argentina

Elateridae | Rt 16 nr. Rio Negro, Chaco Province, Argentina

This is without question a species of click beetle (family Elateridae), but despite its rather distinctive coloration I’ve not found any images that resemble it. I found these beetles fairly commonly on flowers of Solidago chilensis in April 2012 at several localities along Rt 16 in northern Argentina (Chaco Province).

Copyright © Ted C. MacRae 2013

Featured Guest Photo: A Spectacular Case of Mimicry

/ Ted C. MacRae / 9 Comments

On occasion I receive photos from readers that are so remarkable I simply must share them (with the owner’s permission, of course). Recently I received a note from Len de Beer in Maputo, Mozambique, who was looking for help identifying a tiger beetle he had photographed on the beaches of the Maputo elephant reserve. My knowledge of Afrotropical tiger beetles is rudimentary, so I had to tap the expertise of fellow cicindelophile Dave Brzoska for the ID (many thanks, Dave), but in the ensuing correspondence Len sent me the following photograph that he took of another tiger beetle species while living in Madagascar:

The mimic: Peridexia hilaris

The mimic: Peridexia hilaris | Anzojorobe, Madagascar (photo © Len de Beer) 

A spectacular species to be sure, but the story behind its appearance is even more remarkable. This tiger beetle is one of two species in the Madagascan-endemic genus Peridexia, both of which exhibit color patterns that are a near-perfect match for that of the local pompilid wasp, Pogonius venustipennis (see photo below). According to Pearson & Vogler (2001), not only do these tiger beetles share the wasp’s bright yellow and black color pattern, but they also run in constant small circles (rather than the distinct, straight-line sprints that are more typical of tiger beetles) and fly readily when frightened, only to land again on the forest floor. These running and flying behaviors more closely resemble the foraging movements of the wasp than the movements of a typical tiger beetle, resulting in mimicry so effective that even tiger beetle collectors have been fooled and stung on the fingers when they attempted to collect their first Peridexia!

The model: Pogonius venustipennis

The model: Pogonius venustipennis (photo © Len de Beer)

Camouflage is the most widely observed predator avoidance mechanism in tiger beetles, with numerous species known whose color patterns closely resemble or otherwise allow them to blend in with the color and texture of the soils found in their preferred habitats. Nevertheless, mimicry is common enough (although anecdotal evidence still far outweighs true experimental evidence). Pearson & Volgler (2001) list examples of tiger beetles resembling mutillid wasps (commonly called “velvet ants”) from North and South America, as well as India, and also mention a South American tiger beetle species, Ctenostoma regium, that is the same size and shape as Paraponera clavata (or “bullet ant”), a large solitary species that is purported to pack the most painful of all insect stings (that this is true, I am inclined to agree). Tiger beetles can also serve as models—there is a katydid in Borneo whose immatures bear a remarkable resemblance to arboreal species of tiger beetles in the genus Tricondyla (Pearson & Vogler 2001, Plates 26 and 27). It has also been suggested that mimicry in tiger beetles might not be restricted to Batesian associations (unprotected mimic and harmful model) but may also include Müllerian associations (both model and mimic are distasteful or harmful).

My sincere thanks to Len de Beer for allowing me to post his photographs of this remarkable tiger beetle and the wasp it mimics.

REFERENCE:

Pearson, D. L. & A. P. Vogler.  2001. Tiger Beetles: The Evolution, Ecology, and Diversity of the Cicindelids.  Cornell University Press, Ithaca, New York, xiii + 333 pp.

Copyright © Ted C. MacRae 2013 (text)