Month: November 2013

T.G.I.Flyday: Soybean nodule fly

/ Ted C. MacRae / 3 Comments

I’ve been walking the rows of soybean fields for many years now, and while it might seem that I would have very quickly seen all there was to see in terms of insects associated with the crop, this is not the case. The major players are almost always present—lepidopteran caterpillars such as velvetbean caterpillar (Anticarsia gemmatalis) and soybean looper (Chrysodeixis includens), and stink bugs such as southern green stink bug (Nezara viridula), red-banded stink bug (Piezodorus guildinii) and brown stink bugs (Euschistus spp.). However, numerous other insects can be found at one time or another—some of great importance from the perspective of the farmer producer but others with very little impact on the crop. During a tour of soybean fields in Mississippi this past September, I saw a large number of “signal flies”¹ (family Platystomatidae) on the foliage of the soybean plants that I presumed to represent the soybean nodule fly, Rivellia quadrifasciata.²

¹ I originally learned these to be “picture-winged flies”—a name now more commonly used to refer to members of the family Ulidiidae—which I learned as “Otitidae”!

² This species can be separated with certainty from the closely related and largely sympatric species R. colei only by examination of male genitalia (Namba 1956). Rivellia quadrifasciata is more common and widespread than R. colei and is the species cited in literature in association with soybean.

Rivellia quadrifasciata (soybean nodule fly) | Stoneville, Mississipi

Rivellia quadrifasciata (soybean nodule fly) | Stoneville, Mississipi

Rivellia quadrifasciata is widely distributed in the eastern U.S. where it originally fed probably on tick trefoil, Desmodium spp. (Foote et al. 1987), but has since adapted to soybean, Glycines max (Eastman & Wuensche 1977), and black locust, Robinia pseudoacacia (McMichael et al. 1990). Despite its relatively recent adaptation to soybean as a favored host plant, the species does not appear to cause much economic damage to the crop. The small, white, maggot-like larvae live in the soil and feed on the Rhizobium nodules of the roots that are used by the plant for nitrogen-fixation. Soybean, of course, is famous for its compensatory abilities and can withstand considerable nodule injury without yield impact, and as a result losses from this insect are considered minor (Heatherly & Hodges 1998).

Signal flies wave their wings constantly.

The wings of signal flies are almost always in constant motion.

Of more interest from a natural history perspective, these flies—like other members of the Platystomatidae—are almost always seen with their wings in a constant “waving” motion as they walk about on the host leaves. This seems clearly an intraspecific “signaling” behavior (and the source of the family’s common name), with the pattern of markings on the wings and the particular sequence of movements of the wings combining to provide species-specific signals for mate recruitment. Some Asian members of the family are famous for the remarkably elongated eye stalks of the males, which aid in intraspecific male-to-male combat behaviors that provide selection pressure for even more elongate eye stalks. Sadly, our North American species exhibit no such modifications of the head, but their strangely tubular mouthparts do give them the appearance of wearing a “gas mask.”

gas mask

The strangely tubular mouthparts give adults the appearance of wearing a “gas mask.”

Information on the biology of adult platystomatids is limited, but a wide range of adult foods, e.g. nectar, honeydew, plant sap, bird droppings, and carrion, have been reported for this species, and R. quadrifasciata males have been observed to feed females globules of liquid during mating.

REFERENCES:

Eastman, C. E. & A. L. Wuensche. 1977. A new insect damaging nodule of soybeans: Rivellia quadrifasciata (Macquarl). Journal of the Georgia Entomological Society 12:190–199.

Foote, B. A., B. D. Bowker & B. A. McMichael. 1987. Host plants for North American species of Rivellia (Diptera, Platystomatidae). Entomological News 98:135–139 [Biodiversity Heritage].

Heatherly & Hodges. 1998. Soybean Production in the Midsouth. CRC Press LLC, Boca Raton, Florida, 416 pp. [Google Books].

McMichael,  B. A., B. A. Foote & B. D. Bowker, B. D. 1990. Biology of Rivellia melliginis (Diptera: Platystomatidae), a consumer of the nitrogen-fixing root nodules of black locust (Leguminosae). Annals of the Entomological Society of America 83(5):967–974 [abstract].

Namba, R. 1956. A revision of the flies of the genus Rivellia (Otitidae, Diptera) of America north of Mexico. Proceedings of the U.S. National Museum 106:21–84 [Biodiversity Heritage].

Copyright Ted C. MacRae 2013

One-shot Wednesday: Hawk moths suck!

/ Ted C. MacRae / 9 Comments
Hyles lineata nectaring at flowers of Ericameria nauseosa | San Juan Co., Utah

Hyles lineata nectaring at flowers of Ericameria nauseosa | San Juan Co., Utah

I admit it—I give short shrift to Lepidoptera compared to other groups of insects. This is not because I don’t think they deserve attention; they are a stunning group with an amazing suite of adaptations to life on earth. It’s just that they already receive a lot of attention from others, while so many other equally amazing groups of insects remain almost completely unknown and under-appreciated due to the sole fact that they are smaller and less conspicuous. I’m not anti-Lepidoptera; I’m just pro-other Insecta. Every now and then, however, I must give Lepidoptera their due, and since today is Wednesday it’s a good day to feature a hawk moth that I got but a single photograph of on my late August Great Basin collecting trip.

Hyles lineata is not a particularly rare insect—in fact, it is one of the most common and widespread species of hawk moth (family Sphingidae) in North America. What is hard to come by, however, is a good shot of an adult nectaring at a flower. While such shots abound, most feature busy backgrounds and blurred wings. My photo is no different. However, I am a coleopterist, and when I took this shot there were also longhorned beetles present on the same flowers—it could be considered remarkable that I even diverted my attention long enough to attempt a shot. Of course, hawk moths are amazing creatures that have independently arrived at the same flight abilities and feeding habits as the equally amazing but taxonomically distant hummingbirds with their ability to hover motionless while sipping nectar and beating their wings at blinding frequencies. With little time to practice and even less to optimize settings, I’m amazed that I even got an adequate photograph before the moth zipped off to another bush. Yes, hawk moths suck, and that is amazing!

Copyright © Ted C. MacRae 2013

A winter longhorned beetle

/ Ted C. MacRae / 11 Comments

According to the calendar it’s still autumn; however, in practical terms winter has settled in across much of the U.S. For those of us who study wood-boring beetles in the families Buprestidae (jewel beetles) and Cerambycidae (longhorned beetles), our time for collecting ended long ago. Adults of most species are active in spring and early summer, although some species don’t really make their appearance until summer is in full swing and a few rather distinctive species in genera such as Crossidius and Megacyllene make their appearance exclusively during fall. There is one longhorned beetle, however, that can actually be encountered in its greatest numbers during the dead of winter—Rhagium inquisitor, or the “ribbed pine borer.”

Rhagium inquisitor | Reynolds Co., Missouri

Rhagium inquisitor overwintering adult | Reynolds Co., Missouri

Rhagium inquisitor is unique among North American cerambycids in several respects. Most species in the family overwinter as mature or immature larvae, the former triggered to pupation by the first warm days of late winter and early spring in preparation for emergence as adults a few weeks later. Rhagium inquisitor, on the other hand, pupates during late summer and fall and then transforms to the adult before winter sets in (Linsley & Chemsak 1972), passing the winter in this stage and emerging during the earliest days of spring. Also unique among North American cerambycids is the place of pupation—directly under the bark. This contrasts with most other species, which either feed and pupate within the sapwood or feed under the bark but then bore into the sapwood for pupation. The species breeds exclusively in the trunks of dead conifers, with pines (Pinus spp.) especially favored, and as a result one can easily encounter the adults by peeling back the bark of dead pines during winter. Pupation takes place within distinctive rings of frass and coarse, fibrous wood shavings, prepared by the larva prior to pupation, so even when adults and larvae are not present the occurrence of this species can be determined by the occurrence of their pupation rings.

Adults overwinter in cells lined with frass and fibrous wood shavings.

Adults overwinter in cells lined with frass and fibrous wood shavings.

Not only are the overwintering and pupation habits of this species unique, but the adults themselves are distinctive from all other North American cerambycids (Yanega 1996) in their appearance—”big-shouldered” build, heavily “ribbed” elytra, and unusually short antennae (that are anything but “longhorned”). Lastly, the species is distributed not only in the boreal forests of North America, but Europe and Asia as well. The species is extremely variable in size and sculpturing, which combined with its Holarctic distribution has led to an unusually high number of synonyms. In fact, much of the North American literature prior to Linsley & Chemsak (1972) concluding that the North American and Eurasian forms represented the same species refers to this species as R. lineatum.

REFERENCES:

Linsely, E. G. & J. A. Chemsak. 1972. Cerambycidae of North America, Part VI, No. 1. Taxonomy and classification of the subfamily Lepturinae. University of California Publications in Entomology 69:viii + 1–138, 2 plates.

Yanega, D. 1996. Field Guide to Northeastern Longhorned Beetles (Coleoptera: Cerambycidae). Illinois Natural History Survey Manual 6: x + 1–174 [preview].

Copyright © Ted C. MacRae 2013

Q: How do you photograph cactus beetles?

/ Ted C. MacRae / 10 Comments

A: Very carefully!

This past June I went out to one of my favorite spots in northwestern Oklahoma—Alabaster Caverns State Park in Woodward Co. The park, of course, is best known for its alabaster gypsum cavern—one of the largest such in the world—and the large population of bats that occupies it. Truth be told, in my several visits to the park during the past few years I have never been inside the cavern. The draw for me is—no surprise—it’s beetles. On my first visit in 2009 I found what is now known to be one of the largest extant populations of the rare Cylindera celeripes (swift tiger beetle), previously considered by some to be a potential candidate for listing on the federal endangered species list, and last year I found the northernmost locality of the interesting, fall-active jewel beetle Acmaeodera macra. This most recent visit was the earliest in the season yet, and as I walked the trails atop the mesa overlying the cavern I noticed numerous clumps of prickly pear cactus (Opuntia phaecantha) dotting the landscape.

Opuntia phaecantha | Alabaster State Park, Woodward Co., Oklahoma

Opuntia phaecantha | Alabaster Caverns State Park, Woodward Co., Oklahoma

Whenever I see prickly pear cactus anywhere west of Missouri I immediately think of cactus beetles—longhorned beetles in the genus Moneilema. A half-dozen species of these relatively large, bulky, clumsy, flightless, jet-black beetles live in the U.S., with another dozen or so extending the genus down into Mexico and Baja California, and all are associated exclusively with cactus, primarily species of the genus Opuntia. It wasn’t long before I found one, and deliberate searching among the cactus clumps produced a nice series of beetles representing what I later determined as M. armatum. The resemblance between Moneilema spp. and darkling beetles of the genus Eleodes is remarkable, not only in their appearance but also in their shared defensive habit of raising the abdomen when disturbed. The genus has been related taxonomically to the Old World genus Dorcadion, but Linsley & Chemsak (1984) regard the loss of wings and other morphological modifications to represent convergence resulting from the environmental constraints imposed by root-feeding, subterranean habits in arid environments and other situations where flightlessness is advantageous.

Moneilema armatum adult.

Moneilema armatum adult in situ on Opuntia phaecantha pad.

I have encountered Moneilema beetles a number of times out west, including this species in Texas where it is most common, but since I have only been photographing insects for the past few years this was my first  chance to capture cactus beetle images as well as specimens. The above shot, taken with my iPhone, was straightforward enough, but I wanted some real photographs of the beetle—i.e., true close-up photos taken with a dedicated macro lens. I quickly learned that this would be highly problematic—those cactus spines are long and stiff and vicious, and these beetles are no dummies! Clearly their ability to adapt to such a terrifyingly well-defended plant has had a lot to do with the evolution of their slow, clumsy, flightless, you-don’t-scare-me demeanor. Normally when I photograph insects I do a little pruning or rearranging of nearby vegetation to get a clear, unobstructed view of the subject, and sometimes this also involves “pushing” my way into the vegetation to get the most desirable angle on the subject for the sake of composition. Not so here! In my first attempt, all I could think to do was locate a beetle sitting in repose and try to position myself in some way so that the beetle was within the viewfinder and the cactus’ spines were not impaled within my arms! The photo below shows the only shot out of several that I even considered halfway acceptable, but clearly the spines obstructing the view of the beetle were not going to be to my liking.

First attempt - looking down into plant where beetle was first sitting.

First attempt – looking down into plant where beetle was first sitting.

What to do? The beetle was behaving fairly well (i.e., it was not bolting for cover upon my approach), so I pulled out a pair of long forceps (that I carry with me for just such cases) and used them to gently prod the beetle into a more exposed position. The beetle crawled up onto one of the unopened cactus flower buds and perched momentarily, and I thought I had my winner photograph. I crouched down again, was able to get a little bit closer to the beetle than before, and fired a few shots. Looking at them in the preview window, however, left me still dissatisfied—the beetle was no longer obstructed, but the background was still jumbled, messy and dark, making it difficult for the dark-colored beetle to stand out. I would need to think of something else.

Second attempt - looking down on beetle after coaxing it up.

Second attempt – looking down on beetle after coaxing it up.

I actually take a lot of my photos with the insects sitting on plant parts that have been detached from the plant. This allows me to hold the plant in front of whatever background I choose and micro-adjust the position of the insect in the viewfinder for the best composition. This is “easier” (a relative term) with a shorter lens (think MP-E 65-mm) because the lens-to-subject distance matches almost perfectly the distance between my wrist and my fingers, allowing me to rest the camera lens on my wrist while holding the plant part with my fingers to “fix” the lens-to-subject distance. These beetles, however, are much too big for the MP-E 65-mm, so I had to use my longer 100-mm macro lens. The longer lens-to-subject distance does not allow resting the lens on my wrist, so I must come up with other ways of bracing myself and the subject to minimize movement. Detaching the pad on which the beetle was resting (and if you’ve never tried to detach an Opuntia cactus pad from its parent plant while trying not to disturb a beetle sitting on it, I can tell you it is not an easy thing), I also discovered that the pad was quite heavy and that holding it with the same forceps that I had used to prod the beetle (because of its vicious spines) was yet another unanticipated difficulty. I decided the best way to deal with it would be to get down on one knee in front of the plant, rest my arm on my other knee with the cactus pad extending out in front of me, and photograph the beetle with the plant as close in the background as possible to achieve a lighted and colored background that would help the beetle stand out. Following are examples of those attempts.

Third attempt - holding detaching pad with forceps for better view.

Third attempt – holding detaching pad with forceps for better view.

Detached allows even better close-ups.

Detached allows even better close-ups.

Better for sure, especially the latter, closer one. Still, I wasn’t satisfied—the backgrounds still just had too much clutter that detracted from the beetle and complicated the lighting. I decided to go for broke—why not go for the blue sky background, the cleanest, most natural and aesthetically pleasing background possible! This actually was my first thought when I saw the beetles, but I could never find one on a high enough plant that was growing in a situation where I was able to crouch low enough to get the angle with the sky in the background. By this time my arm was quite weak from holding the heavy cactus pad and squeezing the forceps firmly, and as I contemplated how I could possibly hold the pad up towards the sky and take the shots without being able to rest the camera on my arm I had an idea. Why not rest my arm on the camera? Specifically on top of the flash master unit atop the camera. I adjusted the camera settings for blue sky background, positioned the cactus pad in the forceps so that the pad (and beetle) were hanging down from the forceps but still in an upright position, pointed the camera to the brightest part of the sky (a few degrees from the sun), and then held the cactus pad out in front of the camera with my arm resting on the flash master unit. It worked! My arm still got tired quickly and needed frequent breaks, and I had to do a number of takes to get the exposure settings and composition I was looking for, but the photo below represents my closest approach to what I envisioned when I first knelt down to photograph these beetles. A clear view of the beetle, on its host plant, with lots of nice value contrast between beetle, plant and background.

Fourth attempt - holding detached pad up against sky for cleaner background.

Fourth attempt – holding detached pad up against sky for cleaner background.

Once I had the technique figured out, I was able to get some really close-ups shots as well, still, however, with enough blue sky in the background to make it clean and pretty…

Zooming in with sky background gives a nice, clean close-up.

Zooming in with sky background gives a nice, clean close-up.

…as well as playing with some unusual compositions that one can afford to try only after they are confident they have gotten the required shots. I am particularly fond of the following photo, in which the beetle appears to be “peeking” from behind its well-defended hiding place on its host plant.

Having a little fun with the close-ups - he's peaking!

Having a little fun with the close-ups – he’s peaking!

If you have any experiences photographing these or other such “well-defended” insects (without resorting to the white box!) I would love to hear about them.

REFERENCE:

Linsley, E. G. and J. A. Chemsak. 1984. The Cerambycidae of North America, Part VII, No. 1: Taxonomy and classification of the subfamily Lamiinae, tribes Parmenini through Acanthoderini. University of California Publications in Entomology 102:1–258 [preview].

Copyright © Ted C. MacRae 2013

Red-eyed poop!

/ Ted C. MacRae / 9 Comments

I was looking at some of my older files and ran across these photographs taken in early 2011 in Campinas (São Paulo state), Brazil. They’re not my best photos from a compositional and technical perspective, as I was still on the steep part of the learning curve with the Canon MP-E 65mm macro lens. This lens is no doubt powerful and allows amazingly close-up photographs, but it is rather a beast to learn in the field, especially hand-held. I could quibble endlessly about missed focus and suboptimal composition with these shots, and that is probably why they never made it to the front of the line for being posted. Nevertheless, they still depict some interesting natural history by one of nature’s most famous natural history poster children—the treehoppers (order Hemiptera; family Membracidae).

An adult next to a cast nymphal exuvia.

Bolbonota sp. (Hemiptera: Membracidae), upper right | Campinas, São Paulo, Brazil. Note cast exuvia.

The treehoppers shown in these photos were found on a low shrub in a municipal park and are all that I could manage before my clumsy, unpracticed molestations caused the few adults and nymphs present in the aggregation to disperse. The dark coloration of the adult and its globular form, corrugated pronotal surface, and lack of any horns identify the species as a member of the genus Bolbonota in the New World tribe Membracini (another similar genus, Bolbonotoides, occurs as a single species in Mexico). Species identification, however, is much more difficult, as there are at least a dozen species recorded from Brazil and perhaps many more awaiting description. We have a similar though slightly more elongate species here in eastern North America, Tylopelta americana. I don’t know if this is a specific character or not, but I don’t recall seeing any members of this genus with smoldering red eyes—it gives them an almost devilish appearance, especially the blackish adults (see last photo)!

Bolbonota sp. late-instar nymphs clustered together.

Bolbonota and similar genera are often cited by evolutionists as examples of insects that mimic seeds. I can see such a resemblance if I force myself, but honestly I don’t really buy it. To me they seem to bear an uncanny resemblance to the chlamisine leaf beetles which are thought to mimic caterpillar frass. As with the beetles they resemble, frass-mimicry seems to make much more sense than seed-mimicry, especially given their preference for positioning themselves along the stems of the plants on which they feed (when was the last time you saw seeds of a plant randomly distributed along its stems?). Another thought I’ve had is that this is not an example of mimicry at all, but merely an accidental consequence of the heavy, corrugated body form they have adopted, which likely also affords them a reasonable amount of protection from predation. Confounding both of these theories, however, are the radically different appearance and form of the adults versus the nymphs, and indeed even between the different nymphal instars (see early- and late-instar nymphs in photo below). The later instars seem perfectly colored for mimicking unopened leaf buds, but why they would start out dark in early instars before turning mottled/streaked-white as they mature, only to revert back to dark when reaching adulthood, is a mystery to me. If my thoughts are anywhere close to the truth, it would be a remarkable case of different life stages mimicking the products of two different taxonomic kingdoms (plant parts as nymphs, animal poop as adults)!

Bolbonota sp. nymphs tended by Camponotus sp. | Campinas, São Paulo, Brazil.

An ant (presumably Camponotus sp.) tends a first-instar nymph alongside a later instar.

Of course, if either/both of these lines of defense fail then there are the ant associates that often protect treehoppers and other sap-sucking, aggregating insect species in exchange for the sweet, sugary honeydew that such insects exude as a result of their sap-feeding habits. I presume this ant belongs to the genus Camponotus, perhaps C. rufipes or C. crassus which are both commonly encountered treehopper associates in southern Brazil. I have written previously about ant-treehopper mutualism in the stunningly-marked nymphs of another treehopper, Guayaquila xiphias, and its ant-associate C. crassus in Brazil Bugs #15 – Formiga-membracídeos mutualismo (a post that has become one of this blog’s most popular all-time). Maybe this post will never match that one in popularity, but I do find the third photo shown here remarkable in that is shows no less than five elements of this treehopper’s natural history (early-instar nymph, late-instar nymph, cast nymphal exuvia, partial adult, and an ant-associate) within a single frame (shot by a person still on the steep portion of the MP-E 65mm learning curve!).

Copyright © Ted C. MacRae 2013

Hooray for iStock—I finally have an ID for my photo

/ Ted C. MacRae / 16 Comments

I was all set to make a “One-Shot Wednesday” post today, but sometimes big news strikes and plans must change. The news today was in the form of a random tweet by Alex Wild:

iStock-caption_Wild-20131120

The link in the tweet led me to the following photo on iStock by Getty:

bedbug has captured worm

I was stunned—the photo depicted a scene almost identical to one that I had photographed back in September while visiting soybean fields in Louisiana. For two months I sat on the photo with no idea what I was looking at, but now thanks to Alex I have my answer! Compare the above photo with mine below, and you’ll see that everything matches perfectly—I had photographed a “bedbug” that had captured a “worm”!

Podisus maculiventris preying on Chrysodeixis includens larva

bedbug captures a worm

I considered myself to be fortunate, because there was not just one but two different subjects in the photo, and both of them matched perfectly with the subjects shown in the iStock photo. Gotta love the internet—nowadays names for even the most hard-to-identify bugs are just a click away if you know where to look!

</snark>

Of course, the aggressor in both photos is not a “bedbug” [sic for “bed bug”] (order Hemiptera, family Cimicidae) but a stink bug (family Pentatomidae), specifically Podisus maculiventris, or “spined soldier bug”—perhaps the most common predatory stink bug in North Amerca and ranging from Mexico and parts of the West Indies north through the U.S. into Canada. It is a well-known predator of crop pests and, as such, has been imported to several other countries as part of classical biological control efforts. As for the “worm,” in my photo it is a late-instar larva of Chrysodeixis includens, or “soybean looper, and while I haven’t been able to identify the exact species in the iStock photo it is definitely a lepidopteran caterpillar that appears to related to if not in the same family as the soybean looper (Noctuidae). Now, I concede that “worm” is sometimes used for lepidopteran larvae, but one must also concede that in it’s broadest sense “worm” can refer to members of several disparate phyla such as Nematoda (roundworms), Platyhelminthes (flatworms), or Annelida (segmented worms).

This case, of course, just screams for application of the Taxonomy Fail Index (TFI), which scales the amount of error in a taxonomic identification in absolute time against the error of misidentifying a human with a chimpanzee—our closest taxonomic relative. For example, when TFI = 1 the error is of the same magnitude as mistaking a human for a chimp, while  TFI > 1 is a more egregious error and TFI < 1 a more forgivable one. In the case shown here, one must go back to the common ancestor that eventually gave rise to all of the worm phyla and noctuid moths (~937.5 mya). In addition, since there are two subjects in the photo, one must also go back to the divergence of the main hemipteran groups that contain bed bugs and stink bugs (mid-Triassic, ~227.5 mya). This results a whopping 1.165 billion total years of divergence between the identifications assigned to the subjects in the iStock photo and their actual identity. Assuming that chimps and humans diverged approximately 7.5 mya, this gives a TFI for the iStock photo of 155! I haven’t searched thoroughly to determine whether this is a record for the highest TFI in a single photo, but surely it is a strong contender!

Copyright © Ted C. MacRae 2013

The “Dagger Butt Weevil”

/ Ted C. MacRae / 4 Comments

In April 2012 I spent some time in northern Argentina collecting insects, and while collecting was not that great (late in the season after a protracted drought) I saw enough of interest to make it a worthwhile effort. Among the insects that I saw were two species of weevil (family Curculionidae)—one being Eurhinus c.f. adonis () and the other this one, also kindly identified by Charles O’Brien as Erodiscus obidensis (Monte 1944). Both of them were found on flowers of Solidago chilensis growing along the roadside near La Escondida in Chaco Province; however, the two weevils are almost complete opposites in terms of coloration and body form—E. adonis brilliant metallic green and robust chunky, and E. obidensis chestnut-colored and elongate slender.

Erodiscus obidensis (Monte) | Chaco Province, Argentina | Apr 2012

Erodiscus obidensis (Monte) | Chaco Province, Argentina | Apr 2012

An obvious feature of E. obidensis are its two stout spines located at the apices of the elytra. I presume that these serve a defensive purpose to protect them against potential avian or reptilian predators. However, if elytral spines are all that is needed for such then why are these structures not found widely across the order Coleoptera—certainly the potential is there, as many beetles exhibit very small spines at the elytral apices. With enough selection pressure one can easily imagine that larger spines would be selected for. Either the spines also/instead serve some other purpose, or development of spines is more energetically expensive than I am imagining.

What purpose those daggers?

What purpose those daggers?

Compared to most of the insects that I have featured on this blog, I wasn’t able to find much information on this species. It was originally described as Atenistes attenuatus var. obidensis from Óbidos in the Brazilian state of Pará (Monte 1944) and is listed as such in the Blackwelder (1947) catalogue. However, my weevil literature is sparse compared to the other beetle groups with which I am more familiar, and I found nothing else in searches on the web as well. It apparently is already known from Argentina, as it is listed at the website Curculionidae de Argentina (but without any photos). As far as I could tell, these are the first photos of the species to be posted to the web, at least with the associated name. Since so little seems to be known about this weevil, I take it upon myself to give it a common name, and I can’t think of a more amusing and fun-to-say name than the “dagger butt weevil” in reference to its distinctive apical spines.

REFERENCES:

Blackwelder, R. E. 1947. Checklist of the coleopterous insects of Mexico, Central America, the West Indies, and South America. Part 5. Bulletin of the U. S. National Museum 185:765–925 [pdf].

Monte, O. 1944. Sobre coleópteros Otidocephalinae. Revista Entomologia, Rio de Janeiro 15(3):318–320 [abstract].

Copyright © Ted C. MacRae 2013

Sunday scarab: Phileurus valgus

/ Ted C. MacRae / 7 Comments
Phileurus valgus (Linnaeus) | Otter Slough Conservation Area, Stoddard Co., Missouri

Phileurus valgus (Linnaeus) | Otter Slough Conservation Area, Stoddard Co., Missouri

Few beetles enjoy more popularity than the scarabs (family Scarabaeidae)¹, and within that group certainly the members of the subfamily Dynastinae are the most popular of all due to their often enormous size and presence of highly developed horns on the head and pronotum. The largest beetles in the U.S. (at least, by weight)—the Hercules beetles, genus Dynastes—belong to this subfamily, and in the tropical regions of the New World members of the genus Megasoma (literally meaning “giant body”) are among the heaviest-bodied beetles in the world (ironically, the title spot goes to members of the genus Goliathus in the subfamily Cetoniinae). Of course, almost without exception in the insect world exceptions apply, and not all dynastine scarabs are large, heavy-bodied beetles. In fact, members of the genus Cyclocephala are often mistaken for May beetles (subfamily Melolonthinae), while members of the genus represented by the species featured in this post—Phileurus—are sometimes mistaken for smallish “bess beetles” (Odontotaenius disjunctus) in the family Passalidae due to their flattened and parallel-sided body.

¹ Except maybe tiger beetles, jewel beetles, and longhorned beetles (wink!).

This species resembles and is sometimes mistaken for the common "bess bug."

This species resembles and is sometimes mistaken for the common “bess bug.”

Phileurus is a primarily Neotropical genus, with only two species ranging north into the United States and one, P. valgus, occurring broadly in the eastern United States. Despite its broad distribution, P. valgus seems to be more common in the southern part of the country and has been recorded under bark of decaying wood and attracted to lights. Saylor (1948) notes that Richter reared a specimen from a larvae collected in a cavity of a dead basswood (Tilia sp.) tree, and adults have also been reared from larvae collected in a blackjack oak (Quercus marilandica) snag (Taber & Fleenor 2005). The individual featured here was one of several that I found under the lower trunk bark of a large, standing, dead pin oak (Q. palustris) tree growing in a wet, bottomland forest in the Mississippi Alluvial Plain of extreme southeastern Missouri. I have seen this species from time to time over the years—never abundantly—but these are the first that I have seen in a situation other than being attracted to lights. The bark was quite loose and covered wood that was soft and well-decayed, and three adults were found embedded within a granular frass-filled gallery directly beneath the bark. One can presume that larvae could also have been found within the wood had I done a little digging.

The head of this species is adorned with three small cephalic tubercles.

The head of this species is adorned with three small cephalic and one pronotal tubercles.

Taber & Fleenor (2005) also note that adults of this species possess structures known to be used by other beetles for sound production, but they did not say whether they have heard this beetle making sounds. I have never heard sounds from these beetles when handling them, either. This contrasts with true bess beetles, which stridulate to make a “kissing” sound when handled.

REFERENCES:

Saylor, L. W. 1948. Synoptic revision of the United States scarab beetles of the subfamily Dynastinae, No. 4: Tribes Oryctini (part), Dynastini, and Phileurini. Journal of the Washington Academy of Sciences 38(5):176–183.

Taber, S. W. & S. B. Fleenor. 2005. Invertebrates of Central Texas Wetlands. Texas Tech University Press, Lubbock, 322 pp. [preview].

Copyright © Ted C. MacRae 2013