Four-humped Longhorned Beetle

Acanthoderes quadrigibba | Chalk Bluff Natural Area, Arkansas.

On a recent collecting trip, I went over to Chalk Bluffs Natural Area in the Mississippi Alluvial Plain of northeastern Arkansas.  My quarry was a population of Cylindera cursitans (ant-like tiger beetle) that has been reported from the site—one of the only known sites for the species in Arkansas.  While I was there, I noticed some movement on the trunk of a tree, and a closer look revealed that what appeared to be a piece of bark was actually a beetle—a longhorned beetle to be precise.  The elevated gibbosities of the pronotum and white, transverse fasciae of the elytra immediately identify it as Acanthoderes quadrigibba, a not uncommon species in the eastern U.S., but one that I still get excited about whenever I encounter it.

Note the four pronotal ''humps'' in this dorsolateral profile view.

Judging by the number and diversity of plant genera that have been recorded as larval hosts for this species—Linsley and Chemsak (1984) recorded Acer, Betula, Carya, Castanea, Celtis, Cercis, Fagus, Ficus, Quercus, Salix, Tilia, and Ulmus—you could be forgiven for thinking that this is one of the most common and abundant species of longhorned beetle in North America.  I have not found this to be the case, and I don’t think it is because I’m simply missing it due to its cryptic appearance.  Longhorned beetles in the tribe Acanthoderini are, like many species in the family, quite attracted to lights at night, and I’ve done plenty of lighting over the years.  What I have noticed is that nearly all of my encounters with this species have been in the Mississippi Alluvial Plain—an area rich with wet, bottomland forests that contrast markedly from the dry to dry-mesic upland forests that cover much of the southern two-thirds of Missouri.  I’ve also reared the species a few times from Salix, one of the host genera recorded by Linsley and Chemsak (1984).  In both cases, the wood was not freshly dead (as is commonly preferred by many other longhorned beetles), but a little past its prime and starting to get somewhat moist and punky.  In the case of this beetle, I suspect that the nature of the host wood may be more important than the species, the preference being for longer dead wood in moister environments.  Of course, observations by another collector in another state may completely obliterate my idea, but for now it sounds good.

A closeup photograph of the elytral markings of this beetle was the subject of ID Challenge #9, to which a record 18 participants responded (thanks to all who played!).  Troy Bartlett takes the win with 12 points (and attention to detail), while Dennis Haines, Max Barclay, Mr. Phidippus, and Josh Basham all score double-digit points.  Troy’s win moves him into the top spot in the overall standings of the current BitB Challenge Session with 23 pts, but Dave is breathing down his neck with a deficit of just a single point.  Tim Eisele and Max Barclay have also moved to within easy striking distance with 19 and 18 points, respectively, and several others could make a surprise move if the leaders falter.  I think I’ll have one more challenge in the current session before deciding the overall winner—look for it in the near future. 

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.

Copyright © Ted C. MacRae 2011

About Ted C. MacRae

Ted C. MacRae is a research entomologist by vocation and beetle taxonomist by avocation. Areas of expertise in the latter include worldwide jewel beetles (Buprestidae) and North American longhorned beetles (Cerambycidae). More recent work has focused on North American tiger beetles (Cicindelidae) and their distribution, ecology, and conservation.
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8 Responses to Four-humped Longhorned Beetle

  1. Obviously, I have much to learn about beetles, having fallen for the dermestid ruse on this one in the challenge. But as for Troy’s guess on the meaning of the genus name, might I get one extra credit point for noting that it doesn’t mean a “thing of wood”? (I can’t even figure out where that came from.) It means spiny neck, one would suppose in reference to the protuberances of the pronotum.

    • I agree it means spiny neck. “Dero” for neck comes from Greek instead of Latin, so the confusion is understandable.

      You are hereby awarded one bonus point!🙂

  2. I was just guessing on the genus, based on various latin words I plugged into some online dictionaries. Acantho=wood, de=of, res=thing. The order seems wrong now though. It did seem to make sense, given the natural history.

    • “Thing of wood” or not, you still supplied the title of this post!

    • The rules and derivations of biological nomenclature can be arcane, but here is what I would pedantically say to a student who proposed the derivation you gave, Troy.

      “Acanth-” (from Greek, borrowed into so-called New Latin) means spine or thorn (sometimes seta, in entomology), not wood, at least not properly.
      “De” is not Greek, so not likely to be slapped together with “acanth-, and in any case its meaning would be rendered by a connecting vowel or case ending, rather than as a preposition stuck into the middle of a word (even a badly coined one, one would hope).
      “Res” is indeed Latin for thing, but the comment about “de” tells us it does not stand alone, but is part of longer root including the de syllable.

      Thing of wood would be:
      Greek derived — xylopragma
      Latin derived — lignicola, ligneum (or in this case lignea), or most literally but rather clumsily resmateriae

  3. Marvin says:

    I photographed one of these beetles back in June, the one and only I’ve ever seen. It happened to be on the metal frame of our basement door. This is pure speculation, but it could be that all the past-its-prime dead wood left from the severe ice storm of January, 2009, accounted for its presence in north-central Arkansas.

    • Could be – there was a place in the southeastern Missouri Ozarks where I collected tons of wood-boring beetles during the early-mid 1980s. A lake had been constructed there a few years earlier, and the subsequent flooding resulted in a long period of tree decline and death. Blacklighting for cerambycids was always fantastic there in those days, but more recent visits haven’t seemed as productive.

  4. Pingback: Super Crop Challenge #7 « Beetles In The Bush

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