Spiney, scaley distractions

Those who have read this blog for any length of time know that single-mindedness is not one of my shortcomings. I call myself a coleopterist and even go on trips dedicated specifically towards their study, yet find it impossible to ignore the diversity of non-beetle insects that one finds on such trips. It doesn’t stop there—insect diversity is supported by plants, interesting in and of themselves but even more so in the ways they mix and match to form distinct natural communities. And, of course, natural communities are themselves a product of the landscape—soil and terrain, moisture and its timing, elevation and latitude and longitude. Field trips for me are a constant struggle between the inner specialist—wanting to know everything about my chosen niche (beetles)—and outer generalist—wanting to know something about everything else. But wait—that was a decidedly spineless perspective. There are also animals with spines out there. Not nearly as many as those without, mind you, but that just makes them special—more of a treat to be relished when seen, and among the spined it is the reptiles that get me most excited.

Holbrookia maculata (lesser earless lizard)

Holbrookia maculata (lesser earless lizard), female(?) | Union Co., New Mexico.

This post presents a trio of reptiles that distracted my attentions one day during last year’s Great Plains Collecting Trip. We were looking for promising habitat for Prionus longhorned beetles in northwestern New Mexico (Union Co.), where two species (P. fissicornis and P. emarginatus) had been collected recently in the area’s vast shortgrass prairie. Remembering our experience the previous day finding another species (P. integer) and its burrows, we were on the lookout for anything that looked remotely like a “burrow” but found nothing. The stark grassland landscape offered little woody vegetation that made the chances of finding any other woodboring beetles remote, and eventually I became distracted by lizards darting amongst the vegetation around us. The first was one I’d never seen before—the lesser earless lizard (Holbrookia maculata), rather small lizards that were extremely wary, difficult to approach, and quick to dash behind the nearest grass clump. I managed one fairly adequate iPhone photo, but I wanted better photos and had grown weary of finding no beetles so broke out the big camera.

Holbrookia maculata (lesser earless lizard)

Holbrookia maculata (lesser earless lizard), male(?) | Union Co., New Mexico.

I presume the first photo (two above) is a female while the second photo (immediately above) is a male based on the paler coloration and less distinct black markings of the former. The preferred habitat of “relatively level terrain with sparse, low-lying vegetative cover and loose, friable soils” (Degenhardt et al. 2005) describes perfectly the habitat in which we found them. They were extremely difficult to photograph due to their proclivity to hide behind vegetation, and the two photos shown here were about as far in the open as I could get them while trying to approach with the camera.

Crotaphytus collaris (common collared lizard)

Crotaphytus collaris (common collared lizard) | Union Co., New Mexico.

I have loved collared lizards ever since I first photographed a nice, big, colorful male Crotaphytus collaris (eastern collared lizard) in western Oklahoma back in 2009. When I saw this still striking but much less colorful individual, I didn’t know what species it was, but I didn’t think it was the eastern species that I had already encountered not only in Oklahoma but also several times on igneous glades in my home state of Missouri. To my surprise, however, the eastern species is the only one inhabiting New Mexico (Degenhardt et al. 2005)—other species distributed further to the west or south. I had better luck photographing this individual, for even though it occasionally ducked into the vegetation (allowing one charming shot of it peering above the “grass” line—see third photo below) it was also content to stay out in the open along the gently sloped road bank where I had found it and dart from spot to spot between suspicious glares. This particular individual was smaller than the big males I have seen, so I suspect it is either a female or a juvenile.

Crotaphytus collaris (common collared lizard)

Not shy about remaining fully exposed, it clambered atop a rack to watch more carefully.

Degenhardt et al. (2005) mention an interesting factoid about collared lizards regarding the fact that they, unlike many other lizards, do not readily lose their tails (autotomy). Collared lizards are fast runners, often rearing up on their two hing legs, for which an intact tail would be an important organ for maintaining balance. In the case of these lizards, the advantages of rapid locomotion probably outweigh benefits from tail autotomy.

Crotaphytus collaris (common collared lizard)

Peering charmingly above the “grass” line.

While two reptile species at one stop might seem doubly lucky, little did I know a hat-trick still awaited me. We still had no solid evidence to suggest that Prionus beetles were active in the area, but we set out two traps anyway because the soil exposures seemed similar to those we saw the day before and then moved just down the road to where the soils turned redder and seemed to have higher sand content to set one more trap. As Jeff set the trap, my distraction with saurian subjects continued when I ran into a marvelously camouflaged western hognose snake (Heterodon nasicus).

Hognose snake

Heterodon nasicus (western hognose snake) | Union Co., New Mexico.

Western hognose snakes are typically found in grassland habitats with sandy soils (Degenhardt et al. 2005), so the occurrence of this individual at this spot was no surprise. What was a surprise was how strikingly marked this individual looked compared to the other two individuals I’d seen to this point—the first a more subtly marked individual in a rare sand prairie in southeastern Missouri, and the second a more uniformly mottled individual in northwestern Oklahoma’s Salt Plains National Wildlife Refuge. This could be a result of subspecific differences—Missouri populations are assigned to the subspecies H. nasicus gloydi (dusty hognose snake), but I am unsure of the subspecific assignment of the Oklahoma individual. According to Degenhardt et al. (2005) only the nominate subspecies occurs in northern New Mexico (subspecies H. n. kennerlyi can be found in the southwestern part of the state, while intergrades with subspecies H. n. gloydi are said to occur in the extreme southeastern part of the state).

Hognose snake

The strongly upturned rostral (snout) is one character distinguishing the western from the eastern hognose snake.

All species of hognose snakes are famous for their well-choreographed sequence of defensive displays. While they are said to rear up cobra-like and strike out with their mouth open while hissing, I have never seen this behavior by any of the western or eastern hognose snakes that I’ve encountered. The first western individual I saw (in Missouri) insisted on continually trying to burrow into the deep, loose sand and made no other defensive display, while the eastern individual referenced above simply tried to run, although it did eventually barf up a half-digested frog! The individual shown here seemed reticent to do much of anything, remaining coiled up and watching and coiling even tighter as my molestations continued. At last, this one performed some theatrics by writhing in mock agony and then rolling over on its back and playing dead (a behavior called thanatosis). The Oklahoma snake also did this, adding further dramatic value by opening its mouth wide, allowing the tongue to protrude, and ejecting blood from the lacrymal glands while emitting musk from the cloaca. This one didn’t do too much with its mouth, but it did so much more with its cloaca (defecating!). If the idea of eating a snake isn’t revolting enough to begin with, then surely eating a snake covered in crap is!

Hognose snake

The ultimate in thanatotic displays—not only dead, but covered in crap!

In addition to the strongly upturned rostral (snout), best seen in the second photo above (the rostral is only moderately upturned in the eastern species), the black-checkered ventral coloration seen in the third photo confirms this as the western hognose species. The eastern hognose snake is distributed further east and does not occur in New Mexico (Degenhardt et al. 2005).

In an amusing twist to the search for Prionus at this site, while photographing the animal I happened to look down to my side and saw a male Prionus beetle crawling through the vegetation! I recognized the species immediately as P. fissicornis—represented in my cabinet by only a single specimen, and although Jeff and I would find no more after a through search of the area, our traps yielded a “bucket loads” of the beetles the next morning.

REFERENCE:

Degenhardt, W. G., C. W. Painter & A. H. Price. 2005. Amphibians and Reptiles of New Mexico. University of New Mexico Press, 507 pp. [Google Books].

© Ted C. MacRae 2015

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A flower visiting jewel beetle that is not an Acmaeodera

Agrilus muticus

Agrilus muticus LeConte, 1858 | Alabaster Caverns State Park, Woodward Co., Oklahoma

In North America, jewel beetles (family Buprestidae) routinely associated with flowers usually belong to the genus Acmaeodera. Often black with yellow and/or red elytral markings (e.g., A. immaculata, A. macra, A. ornataA. neglecta, A. tubulus, etc.), these beetles are especially diverse in western North America and bear a striking resemblance to stinging bees and wasps (maintaining the charade even during flight by holding their fused elytra together above the abdomen). A few other less speciose genera (e.g., Anthaxia and Agrilaxia) also regularly visit flowers, but for the most part outside of these genera encounters on flowers are at best incidental.

Agrilus muticus

Adults are associated almost exclusively with flowers of winecup (Callirhoe involucrata).

Of course, exceptions are the rule in biology, and in the genus Agrilus there are few species that are found almost exclusively on flowers. One of these, Agrilus muticus occurs in Texas, Oklahoma, and Kansas and has been found only in the flowers of winecup, Callirhoe involucrata (Fisher 1928). The species is fairly routinely encountered wherever these plants are found in bloom, and I have observed adults in these flowers on numerous occasions feeding on the petals and mating (and see this BugGuide photo of group sex!). While winecup can be presumed to be the larval host, it has never been reared from this (or any other) plant, and in fact I am not aware of anything beyond descriptions and catalogue listings that have been published for the species. I suspect the larvae tunnel within the stem base or main roots of living winecup plants (and, thus, making them more difficult to rear than species associated more typically with dead wood).

Only one other North American Agrilus has been documented routinely visiting flowers. Agrilus blandus is frequently encountered on flowers of Eriogonum, and these plants have also been confirmed as larval hosts (Nelson & Westcott 1976). None of the remaining species of Agrilus in North American are known to routinely visit flowers, and in fact the vast majority of them are associated with woody rather than herbaceous plants. The latter include A. concinnus, which breeds in the base of living Hibiscus (MacRae 2006), and A. malvastri, which is usually found on Sphaeralcea (Fisher 1928), although whether that plant also serves as the larval host remains unconfirmed. It is interesting that most of these non-woody plant hosts (CallirhoeHibiscus and Sphaeralcea, but not Eriogonum) all belong to the same plant family—Malvaceae. Plants in this family also serve as known or suspected larval hosts for several species of jewel beetles in the genus Paragrilus—a close relative of the genus Agrilus. Again, these beetles are normally found on the foliage and not on the flowers.

REFERENCE:

MacRae, T. C. 2006. Distributional and biological notes on North American Buprestidae (Coleoptera), with comments on variation in Anthaxia (Haplanthaxia) viridicornis (Say) and A. (H.) viridfrons Gory. The Pan-Pacific Entomologist 82(2):166–199 [pdf].

Nelson, G. H. & R. L. Westcott. 1976. Notes on the distribution, synonymy, and biology of Buprestidae (Coleoptera) of North America. The Coleopterists Bulletin 30(3):273–284 [pdf].

Fisher, W. S.  1928. A revision of the North American species of buprestid beetles belonging to the genus AgrilusU. S. National Museum 145, 347 pp. [Smithsonian Libraries].

© Ted C. MacRae 2015

Posted in Buprestidae, Coleoptera | Tagged , , , , , , | 4 Comments

Crypsis? Mimicry? Crypsimicry?

Continuing with the previous post’s theme on crypsis, here is an interesting insect that I photographed in north-central Oklahoma in late June 2014. I was checking standing and fallen trunks of large, dead eastern cottonwood (Populus deltoides) trees in Woods Co. near the Cimarron River, where just a few days earlier I had found a jewel beetle (family Buprestidae) that had eluded me for more than 30 years—Buprestis confluens. I had found only a single individual and returned to the spot in the hopes of finding more. As I searched the trunk of one particularly large, fallen tree—its trunk still covered with bark, I noticed movement but couldn’t make out right away what I was seeing. A closer look revealed the movement to be from a wasp-like insect, its antennae curiously quivering in a manner that reminded me of an ensign wasp (family Evaniidae). More careful looking, however, revealed the insect to be not a wasp, but a longhorned beetle (family Cerambycidae), which I then recognized to be the species Physocnemum brevilineum.

Physocnemum brevilineum

Physocnemum brevilineum (Say, 1824) on fallen cottonwood (Populus deltoides) | Woods Co., Oklahoma

This beetle is commonly referred to as the elm bark borer, a reference to the larval habit of mining within the bark of living elm trees, but as far as I can tell this beetle is anything but common. Like the Buprestis confluens that I had found a few days earlier, this was a species known to me only by pinned museum specimens (I’m always amazed when a woodboring beetle species is apparently common enough to warrant a common name and is said to reach pest status in some cases, yet eludes my net for decades!). At any rate, my impression based on these pinned specimens and published images was that the species is another of the many longhorned beetles that seem to mimic ants (Cyrtinus, CyrtophorusEudercesMolorchus, and Tilloclytus being among the others). Like many of these other mimics, the species is dark with small amounts of red and bears polished, ivory-colored ridges at mid-elytra to give the illusion of a narrow waist. After seeing a living individual, however, and especially its behavior—in particular the very wasp-like manner in which it moved its antennae, I’m not so sure that ant mimicry alone explains the appearance and behavior of the species.

Physocnemum brevilineum

A lateral view reveals the beetle, but is it trying to mimic an ant, or a wasp, or both?

Of course, there is no reason why it must be ant mimicry or wasp mimicry (or crypsis, for that matter). Evolution has no rule stating that only one survival strategy can be employed at a time, and if, as it seems to me, the beetle is utilizing both crypsis and mimicry—the first to avoid detection and, failing that, the second to give the potential predator pause, then there is no reason why the mimicry portion of its defense couldn’t be modeling both ants and wasps as a way to maximize an overall “nasty hymenopteran” appearance.

© Ted C. MacRae 2015

Posted in Cerambycidae, Coleoptera | Tagged , , , , , , , , , | 4 Comments

Redux: Now you see me…

Chalcophora virginiensis

Chalcophora virginiensis (Drury, 1770) | vic. Calico Rock, Arkansas

…now you don’t!

Chalcophora virginiensis

Chalcophora virginiensis (Drury, 1770) | vic. Calico Rock, Arkansas

Chalcophora virginiensis (Drury, 1770) is the largest jewel beetle (family Buprestidae) in eastern North America. This beetle is also known as the “sculptured pine borer”, and its easy to see why—its hyper-sculptured, shiny metallic body glitters like a jewel in the sunlight! This feature is typical of many species in the family and, in fact, is the source of the family’s other common name—metallic wood boring beetles.

Such dramatic sculpturing and coloration makes cabinets of jewel beetle specimens among the most beautiful in any museum, and for those who have only seen these beetles as pinned specimens in cabinets it can be hard to imagine what purpose such appearance serves. In its native habitat, however, on native host plants, the reason becomes clear. Rather than conspicuous and easily seen, such coloration actually helps the beetle to blend in with its environment and become almost invisible. Measuring well over an inch in length and possessing no other way of defending itself by biting, stinging, or even just tasting bad, these beetles would be a more than healthy snack for almost any avian or reptilian predator, and going about their activities during the day right under the noses of all these visually based predators makes finding mates and oviposition sites an even riskier proposition. For them, the best way to beat a visual predator is to become… invisible! The two photos above show just how dramatic a difference the substrate plays in allowing these beetles to practice their disappearing act. Land on the trunk of a dead or dying pine tree, its aged bark flaked and graying, and the sculpturing and coloration are a perfect match. Land, however, on a healthy tree, its resin-filled bark bright and full of color, and it suddenly becomes a sitting duck. It’s in the beetle’s best interest to be good at telling the difference between thrifty and unhealthy trees, which they do by “smelling” volatile chemicals emitted by trees under stress.

Those interested in more information on this species and its close relatives may wish to consult the recent review of the genus in North America by Maier & Ivie (2014) (see my review of this excellent paper here).

REFERENCE:

Maier, C. A. & M. A. Ivie. 2013. Reevaluation of Chalcophora angulicollis (LeConte) and Chalcophora virginiensis (Drury) with a review and key to the North American species of Chalcophora Dejean (Coleoptera: Buprestidae). The Coleopterists Bulletin 67(4):457–469 [abstract].

© Ted C. MacRae 2015

Posted in Buprestidae, Coleoptera | Tagged , , , , , , , | 5 Comments

Spring beetles on Coreopsis flowers

Abby Lee, Ryan Fairbanks, Stephen Penn atop a rhyolite glades

The WGNSS Entomology Group takes in the view of rhyolite glades from atop Hughes Mountain.

Each spring the Entomology Group of the Webster Groves Nature Study Society takes a field trip to one of the many natural areas outside of the St. Louis area. This year the destination was Hughes Mountain Natural Area, about 75 miles SSW of St. Louis in Washington Co. I especially looked forward to going there this spring, as my last visit to the area was close to 20 years ago. Despite the long absence, I vividly recalled the spectacular vistas from atop the mountain of rhyolite and the diversity of unique plants and insects in the igneous glades that flanked its slopes. When we arrived, we found the glades ablaze with spring wildflowers in full bloom, the most prominent of which was lance-leaved coreopsis (Coreopsis lanceolata). As one of the so-called “yellow composites”, coreopsis is a favored source of pollen and nectar for a variety of insects, including beetles and especially the jewel beetles that I find so interesting.

Acmaeodera neglecta

Acmaeodera neglecta Fall, 1899

Species in the genus Acmaeodera are incredibly diverse in the southwestern U.S. (nearly half of the ~150 species/subspecies known from the U.S. occur in Arizona), where they are usually encountered on a variety of flowers. It is my opinion that the adult beetles mimic small bees, especially in flight by virtue of their fused elytra that do not separate during flight as in most other beetles and thus results in a profile resembling that of a small sweat bee (family Halictidae). The diversity of Acmaeodera drops off considerably in the eastern U.S., with only three species occurring broadly in the area. Missouri is a bit luckier than most eastern states, as two additional species found primarily in the south-central U.S. also occur here (MacRae 1991). One of these is Acmaeodera neglecta Fall, 1899. This tiny species (adults measure only 4–6 mm in length) is very similar to the much more common and widespread A. tubulus (Fabricius, 1801) (see photos here), and in fact its resemblance to that species is so great that it remained unreported from Missouri until Nelson (1987) recognized it among material that I had collected and sent to him during my early collecting days. Acmaeodera neglecta can be distinguished from A. tubulus by the elytra with slightly larger punctures and duller surface and the spots usually longitudinally coalesced into an irregular “C”-shaped marking on each side. I find this species most often in glade habitats.

Acmaeodera ornata

Acmaeodera ornata (Fabricius, 1775)

Acmaeodera ornata (Fabricius, 1775) is more widespread than A. neglecta (although not nearly so commonly encountered as A. tubulus). This handsome species is distinctly larger than A. tubulus and A. neglecta, usually around 8-11 mm in length, and has a broader, more flattened appearance with a distinct triangular depression on the pronotum. The elytra have a bluish cast rather than the bronzy sheen of A. tubulus and A. neglecta, and the spots on the elytra are smaller, more numerous, and more of a creamy rather than yellow color. No other species in the eastern U.S. can be confused with it, although there is a very similar species (A. ornatoides Barr, 1972) that occurs in Oklahoma and Texas. I have encountered this species numerous times on a variety of flowers in Missouri but have never managed to rear it, and in fact larval hosts remain unknown with the exception of one very old (and unreliable) report of the species breeding in hickory (Carya) and black-locust (Robinia).

Valgus canaliculatus

Valgus canaliculatus (Olivier, 1789)

As a general rule, beetles in the family Scarabaeidae don’t visit flowers—species in the subfamily Cetoniinae being a significant exception. This tiny representative of the subfamily, Valgus canaliculatus (Olivier, 1789), is no larger than the Acmaeodera neglecta adult above by length, although the body is broader and strongly flattened. This species is a representative of the tribe Valgini, one of only two tribes in the family that possess dorsal and ventral scale-like setae (the unrelated tribe Hopliini, or monkey beetles, being the other) (Jameson & Swoboda 2005). It has been suggested that the setae might play a role in crysis or adaptive coloration, and even more interesting is the association of most New World species with termites. Eggs are laid in termite galleries and the larvae feed on the wood within the galleries, but it remains unclear whether the termophily is obligatory or the beetles are simply taking advantage of the stable environment and accessible food source offered by termite colonies. Like other species in the subfamily, the adults are fond of flowers; however, only male valgines visit flowers, using specially modified, brush-like mouthparts to lap up nectar. As far as has been determined, the males do not feed on pollen.

Valgus canaliculatus

Note the flattened, scale-like setae covering both the dorsal and ventral surfaces as well as the legs.

REFERENCES:

Fall, H. C.  1899. Synonpsis of the species of Acmaeodera of America, north of Mexico. Journal of the New York Entomological Society 7(1):1–37 [pdf].

Jameson, M. L. & K. A. Swoboda. 2005. Synopsis of scarab beetle tribe Valgini (Coleoptera: Scarabaeidae: Cetoniinae) in the New World. Annals of the Entomological Society of America 98(5):658–672 [pdf].

MacRae, T. C. 1991. The Buprestidae (Coleoptera) of Missouri. Insecta Mundi5(2):101–126 [pdf].

Nelson, G. H. 1987. Additional notes on the biology and distribution of Buprestidae (Coleoptera) in North America, II.   The Coleopterists Bulletin 41(1):57–65 [pdf].

© Ted C. MacRae 2015

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A cicada that snaps, crackles, and pops!

Last summer during a collecting trip through the western Great Plains, field partner Jeff Huether and I made a quick stop in the foothills of the Rocky Mountains just a few miles north of the Colorado/New Mexico state line. Most of the woody vegetation turned out to be New Mexico locust (Robinia neomexicana), which can be a good host for certain species of jewel beetles and longhorned beetles, and since it was mid-late June the timing was also right (assuming there had been good rains in the area). We began beating branches, picking up regular numbers of small longhorned beetles in the genus Sternidius and jewel beetles in the genus Agrilus—nothing unexpected. As I was beating I happened to notice a cicada sitting in a branch in a nearby tree. Usually I don’t see cicadas until they take flight after I unknowingly approach them—more often than not also letting out a metallic screech as they take flight if they are male, and even if I do see them beforehand I rarely am able to get close enough to attempt capture, much less photography. Perhaps the morning temps still had not risen to a point sufficient for the more active behaviors with which cicadas are usually associated.

Platypedia putnami

Platypedia putnami | Las Animas Co., Colorado

The slender, hairy, black body, orange highlights and pronotal collar, and black eyes identify this as a member of the genus Platypedia, and while the genus is large—21 species and four subspecies in western North America (Sanborn & Phillips 2013), its gestalt and occurrence in south-central Colorado make P. putnami the likely choice. Cicadas, of course, are famous for their singing abilities, which is most commonly accomplished through the use of structures at the base of the male abdomen called timbals (or ‘tymbals’). These paired, ribbed membranes make a loud click when buckled, and the male uses musculature to rapidly and rhythmically buckle/unbuckle the timbals to produce their characteristic song (Young & Bennet-Clark 1995). Cicadas of the genus Platypedia, however, belong to a group of genera that have lost the ability to produce sound through timbal organs, instead communicating through an alternate mechanism of sound production called crepitation where the wings are snapped together above the body or banged against the body or on vegetation (Sanborn and Phillips 1999). (Think of the snapping sound that some grasshoppers make as they fly, which is produced by the same mechanism.) You can hear the sound (I can’t really call it a ‘song’) and see a collection of videos of these cicadas at Cicada Mania.

Of course, replacement of one sound production mechanism by another begs the question—is there a selective advantage to sound production by crepitation over timbals? The fact that females also produce sound by crepitation hints at one possible advantage—2-way communication between males and females may provide another mechanism for minimizing the chance of interspecies mate selection, in contrast to the one-way communication (from males to females) that occurs in species that use timbal organs. It is also possible that crepitation is metabolically more efficient than timbal singing, although experimental comparisons of the energetic cost of crepitation versus timbal singing in cicadas are lacking (Sanborn & Phillips 1999).

REFERENCES:

Sanborn, A. F. & P. K. Phillips. 1999. Analysis of acoustic signals produced by the cicada Platypedia putnami variety lutea (Homoptera: Tibicinidae). Annals of the Entomological Society of America 92:451–455 [pdf].

Sanborn, A. F. & P. K. Phillips. 2013. Biogeography of the cicadas (Hemiptera: Cicadidae) of North America, north of Mexico. Diversity 5(2):166–239 [abstractpdf].

Young, D. & H. C. Bennet-Clark. 1995. The role of the tymbal in cicada sound production. The Journal of Experimental Biology 198:1001–1019 [pdf].

© Ted C. MacRae 2015

Posted in Cicadidae, Hemiptera | Tagged , , , , , , , , | 3 Comments

Why is this male carrion beetle “biting” one of the female’s antennae?

American carrion beetles (Necrophila americana) aggregating at sap flow on the trunk of an oak (Quercus sp.) tree.

American carrion beetles (Necrophila americana) aggregation at sap flow on trunk of oak (Quercus sp.) tree.

Earlier this spring I came upon an interesting aggregation of insects at a sap flow at the base of the trunk of a large oak (Quercus sp.) tree. Sap flows are famous for the diversity of insects that are attracted to them (e.g., see my previous post, Party on a pin oak), although the mix of species present can vary from sap flow to sap flow. In this case, the majority of insects present were American carrion beetles (Necrophila americana)¹ (order Coleoptera, family Silphidae), a species encountered much more often on animal carcasses (in fact, the genus name literally translates to “attracted to corpses“) but also occasionally attracted to sap flows (Evans 2014). This is not surprising to me, as I have seen adults regularly in the fermenting bait traps (Champlain & Knull 1932) that I have set out over the years (although I have been unable to find any reference to such attraction in the literature). I had never seen such an aggregation of these beetles before or even yet had the chance to photograph them (although I have photographed its Ceti Eel-like larva), so I paused to setup the camera and take a few photographs.

¹ Not to be confused with the federally endangered American burying beetle (Nicrophorus americanus).

Necrophila americana mating pair.

Necrophila americana mating pair.

Among the many single adults present was a mating pair, which I selected as my subjects. As I was photographing the pair, I noticed the male had a firm grasp of one of the female’s antennae within his mandibles. As I watched them through the lens, I saw the male suddenly release his hold of the female’s antenna, move backward on top of her, and begin using his own antennae to stroke her pronotum (sadly I was unable to snap a photograph at that time). As suddenly as he had released it, the male moved forward and grabbed hold of the female’s antenna once again. It seemed unlikely to me that this represented an act of aggression, but instead must be an important part of their courtship behavior. The female, for her part, did not seem to be bothered too much by the grasping and continued to slowly lumber about around the sap flow as the male went through his routine under my voyeuristic watch.

The male has a firm grasp of the female's antenna.

The male has a firm grasp of the female’s antenna.

Intrigued by this behavior, I searched for other photos of mating/coupled carrion beetles—easy to do considering the many pages of photographs of this species at BugGuide. While the great majority of those photos are of individual beetles, I found this photo and this one of coupled pairs, each also clearly showing the male firmly grasping one of the female’s antennae with his mandibles. Neither photo makes mention of the antennal grasping, but a little further searching did turn up this YouTube video of coupled American carrion beetles, again clearly showing the male grasping of the female’s antenna and even leading the videographer to comment, “Disturbingly, it even appears that this male is threatening to lop off the female’s left antenna if she refuses to mate!” Of course, retribution seems not to be a common behavior among insects, and in looking into this further I found a short note by Anderson (1989) in which the behavior is recorded not only for N. americana but also another silphid, Oiceoptoma noveboracense. Apparently mating actually occurred during the time the male had released his hold of the female’s antenna and was stroking her pronotum with his antennae. He further noted that the antennal grasping behavior continues until eggs and larvae are present at a carcass, at which time it is no longer observed. This suggests that the behavior represents an especially proactive form of “mate guarding” by which males actively ensure their paternity of the offspring of the particular female with which they were mating.

REFERENCES:

Anderson, R. S. 1989. Potential phylogenetic utility of mating behavior in some carrion beetles (Coleoptera: Silphidae: Silphinae). The Coleopterists Bulletin 43(1):18 [pdf].

Champlain, A. B. & J. N. Knull. 1932. Fermenting bait traps for trapping Elateridae and Cerambycidae (Coleop.). Entomological News 43(10):253–257.

Evans, A. V. 2014. Beetles of Eastern North America. Princeton University Press, Princeton, New Jersey, 560 pp. [Google Books].

© Ted C. MacRae 2015

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