Monday Ménage – Brachyleptura rubrica

Photo details: Canon 100mm macro lens on Canon EOS 50D, ISO 100, 1/250 sec, f/18, MT-24EX flash w/ Sto-Fen diffusers.

This mating pair of longhorned beetles represents Brachyleptura rubrica, one of several so-called “flower longhorns” (including the rare Typocerus deceptus) that I saw on flowers of Hydrangea arborescens last June at Trail of Tears State Park in southeastern Missouri.  Flower longhorns collectively represent the subfamily Lepturinae, which among the Cerambycidae are distinguished by their posteriorly tapering elytra and generally narrow pronotum that give them a rather broad-shouldered look.  Their conical coxae (basal segment of the leg) and eyes that usually do not surround the base of the antennae distinguish them from the subfamily Cerambycinae, and the prognathous (forward slanting) face distinguishes them from the Lamiinae (flat-faced longhorns).  Additionally, a great majority of Lepturinae are diurnal (active during the day) and visit flowers as adults, whereas most other Cerambycidae (with notable exceptions) are nocturnal and seldom active during the day (most often being encountered by their attraction to lights).  The subfamily is named for its type genus, Leptura — derived from the Greek word λεπτός (leptos), or narrow, which I presume to be a reference to their relatively more slender appearance compared to other Cerambycidae.  Species in the genus Brachyleptura are distinguished from other Lepturinae by their often abbreviated elytra (“brachy” derived from the Greek word βραχύς, or short), although this is only scarcely the case in B. rubrica.  I’m confident most of you can determine the derivation of the species name.

Although fairly widespread across the eastern U.S., I can remember being really excited the first time I saw this species back in the mid-1980s when I was beginning my faunal study of the Cerambycidae of Missouri (MacRae 1994).  It is by no means rare, but at the same time it is not so routinely encountered as other common flower longhorns in the state such as Strangalia famelica solitaria, S. luteicornis, S. sexnotata, Typocerus octonotatus, and T. velutinus.  Unlike those more commonly seen species, B. rubrica shows a distinct preference for plants with white, compound, flat-topped floral structures.  No plant in Missouri meets this description better than Hydrangea arborecens, and it is on flowers of this plant that I have most often seen the species.  Other flowers on which I have collected it include Ceanothus americanus, Cornus drummondiiDaucus carota, and Parthenium integrifolium — all white, compound, and (except Ceanothus) flat-topped.  Larvae have been recorded breeding in a variety of hardwood species such as beech, birch, elm, hickory, and maple; however, I have only reared this species once — a single individual that emerged from a rather punky dead branch of Carpinus caroliniana (blue beech, musclewood, hornbean) (MacRae and Rice 2007).  I suspect that the condition of the wood (slightly decayed rather than freshly dead) is more important than the actual tree species (although perhaps it is confined to hardwoods and does not utilize conifers).

There is a related species in Missouri, Brachyleptura vagans, which resembles B. rubrica in form and by its white-annulated antennae, but it is distinguished by the elytra being wholly black except for small (usually) red patches behind the humeri (shoulders).  I haven’t encountered this species quite as commonly in Missouri, mostly in shortleaf pine (Pinus echinata) forests of the Ozark Highlands.  I’ve collected it on most of the same flowers as B. rubrica, but rather than H. arborescens it seems to be most fond of C. americanus.

REFERENCES:

MacRae, T. C. 1994. Annotated checklist of the longhorned beetles (Coleoptera: Cerambycidae and Disteniidae) known to occur in Missouri. Insecta Mundi 7(4) (1993):223–252.

MacRae, T. C. and M. E. Rice. 2007. Distributional and biological observations on North American Cerambycidae (Coleoptera). The Coleopterists Bulletin 61(2):227–263.

Copyright © Ted C. MacRae 2010

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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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12 Responses to Monday Ménage – Brachyleptura rubrica

  1. Art Evans says:

    Nice article and photo Ted! I just entered the collection data last night for the first specimens of B. rubrica that I have ever collected. They were in a Malaise trap in Wise County in southwest Virginia.

  2. jason says:

    They’re quite stunning in perfectly subtle ways (though I like flashy critters, I’m equally enamored of the understated beauty that often goes unseen or worse, ignored). And they’re a saucy pair to boot! Catching them “in the act” (of anything: hunting, eating, mating, whatever) offers a sense of life in progress. Great shot!

    And let me add this: I realize beetles are a large group and that insects as a whole might never be fully understood due to the vastness of their numbers. It’s daunting to think more than half the planet’s biomass is tied up in one class of animal. It’s therefore a great deal of fun to read your findings on these species; not only that, but it’s educational–and the sense I get is that I’m learning right along with you as you study and research and try to fill in the abyssal gaps in our collective understanding. Thank you!

    • I appreciate your comments, Jason. You really are learning right along with me on many of the topics I post about.

      Yes, the gap in our knowledge is abysmal – not only with beetles but with natural history in general. All we can do is figure things out one piece at a time. If I know more today than I did yesterday, then it was a good day!

  3. Hi Ted – I really appreciate your parenthetical definitions of the terms you use to describe the beetles in this post. Having the photo right there is extremely helpful as well. The traits that you describe also help me to understand what you look at to distinguish one species (or sub-species, or sub-sub-species🙂 ) from another.

    I thought of you today when I ordered not only the Peterson’s guide to beetles, but Pearson’s guide to Tiger Beetles. What have you done to me?!

  4. Hi there Ted

    A lovely photo as usual! Looks as though the beetles are having a great time mating and eating!

    Best regards, Trevor

  5. Ted, Yes! But its only great if you can get both! Ha ha!

  6. Pollinator says:

    What is the name of the gelatinous structure that is connecting their genitals? I used to know it and I can’t remember. How frustrating.

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