North America’s itsiest bitsiest longhorned beetle

Longhorned beetles (family Cerambycidae) are generally regarded as medium to large-sized beetles, but that doesn’t mean the family is without its pip-squeeks! There are a number of species, primarily in the tribes Tillomorphini, Anaglyptini, and Clytini (all in the subfamily Cerambycinae) that are remarkably effective mimics of ants. Some of these, especially members of the genus Euderces, are quite small, but none are smaller than the absolutely diminutive Cyrtinus pygmaeus. Measuring only 2–3 millimeters in length, the adult beetles can be found on dead twigs and branches among equally small ants such as Lasius americanus.

Cyrtinus pygmaeus | Stoddard Co., Missouri

Cyrtinus pygmaeus | Stoddard Co., Missouri

The species is said to be widespread across eastern North America, having been recorded on a number of hardwood trees (Lingafelter 2007). I have no reason to doubt this, having reared a number of individuals from dead branches of river birch (Betula nigra), chinquapin oak (Quercus muhlenbergii), willow oak (Q. phellos) and black oak (Q. velutina) (MacRae & Rice 2007), but in the wild I have only encountered the species three times—each time as a single specimen that I noticed crawling on my arm after a bout of beating a variety of dead branches. The most recent occasion was two weekends ago during a visit to the Mississippi Lowlands of southeastern Missouri. I had done a bit of beating in a forest dominated by black oak, blackjack oak (Q. marilandica), and southern red oak (Q. falcata) and not found much when I felt a “tickle” on my right forearm. I looked down and was just about to flick the “ant” off my arm when something about the way it moved gave me pause. I stopped and looked closer, then recognizing what it was, instinctively called out “Oh cool, Cryrtinus pygmaeus!” My field partners for the day had never seen the species, so I let them look before I placed it in a vial. I was sure they would ogle at the incredibly tiny longhorned beetle, but their subdued “Hmm”s makes me think they were less impressed with the find than I was.

Cyrtinus pygmaeus

Like other ant-mimicking genera, the elytra of this species bear two prominent humps near their bases.

If the species is so common, why have I not seen them more commonly or on the beating sheet proper as soon as I beat them from their host plant? The answer, I believe, is that they are such effective mimics of the tiniest of ants that I simply overlook them! The series of specimens retrieved from my rearing cans could not be missed, as I combed through the contents every week during the beetle emergence period to make sure I found anything—longhorned beetle or otherwise—that emerged from the wood inside. In the field, however, my search image is queued for more “normal-sized” beetles and especially movement. Most other ant-mimicking longhorned beetles, even though they look very much like ants, still run like longhorned beetles—swiftly, almost frenetically, looking for the earliest opportunity to spread their elytra and take wing. Cyrtinus pygmaeus, on the other hand, is slow and clumsy, not a runner at all (slower even than the ants they mimic). If the three individuals I’ve encountered in the wild to date hadn’t happened to fall on my arm rather than the beating sheet and gotten stuck in my hair and perspiration I may never have noticed them.

Cyrtinus pygmaeus

Bands of white pubescence on the bases of the elytra give the illusion of a narrow-waisted ant.

I considered putting the beetle on a branch for photographs as soon as I found it, but since I had already pulled it off my arm I had already lost the chance to take true field photographs. Instead, I placed the beetle live in a vial and photographed it the next day at home. All of the photos were taken hand-held with an MP-E 65 mm macro lens at the upper end of its magnification capabilities. The green background is simply a colored file folder placed about four inches behind the beetle as I photographed it.

p.s. can you tell me what unusual feature this particular individual exhibits?

REFERENCES:

Lingafelter, S. W. 2007. Illustrated Key to the Longhorned Woodboring Beetles of the Eastern United States. Coleopterists Society Miscellaneous Publications, Special Publication No. 3, 206 pp.

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 2013

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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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22 Responses to North America’s itsiest bitsiest longhorned beetle

  1. Jeff Weber says:

    It has the eyes completely split by the antennae into four separate segments. Is that it?”

  2. Jon Quist says:

    How about those horns on the elytra??

  3. Ani says:

    The unusual feature for me is that a long-horn beetle mimics an ant! I did not imagine them to be so tiny before! Must keep a lookout here as well

    • The tribe (so far as I know) is restricted to the Western Hemisphere. However, there may be members of the tribes Tillomorphini or Anaglyptini in your part of the world. Lots of our ant mimics in the Tillomorphini are flower feeders, so that might be a place to look.

  4. Howdy Ted — Lasius americanus is, for the moment, officially in synonymy with the Eurasian (currently Holarctic) L. alienus. Intuitively, it seems to me they are distinct species, but for now, we have the taxonomy we have.
    Two questions:
    - Where did you find that name?
    - More important, do the beetles run with the ants or feed among them?

    • The ant name info comes from a 1959 review article on the ecology of Cerambycidae – I’m not surprised the nomenclature has changed since then.

      My understanding is that the adults have been found in the company of the ants, but again the only adults I’ve seen in the wild were on my forearm!

  5. Cool beetle! I had no idea cerambycids came that small. What’s that elongate whitish object on its right elytron (that’s not the unusual feature you have in mind, is it?)?

    • Mark Fox says:

      I’m looking at that too, Charley. Could it be a mite? I know the bigger longhorns are often festooned with phoretic mites, could the same be true for this tiny one?

      • Yes, that mite be it. :) I’ve seen lots of phoretic mites on cerambycids, but they are usually red – this one strikes me as more parasitic than phoretic. Nevertheless, I didn’t find any references to parasitic mites on cerambycids in my cursory search of the literature.

    • I think you mite be onto something… :)

  6. 6legs2many says:

    What a cutie! It’s hard to imagine such a tiny cerambycid. I’d love to see a picture of one with something for scale.
    I’m super curious to know what the unusal feature is.

    • I had my lens set to 4-5X for these shots, if that gives you some idea on the size. They are super tiny!

      • Lance - Pest Control says:

        I agree with 6legs, it’d be great to see a comparison shot! They must be incredibly tiny. A very interesting specimen for sure. Thanks for posting such great photos!

  7. I don’t know how, but I actually didn’t know that there were beetles that mimic ants! I understand your experience with unenthused companions after an exciting mimic find – after happening upon some spider ant-mimics in the field for the first time recently, I excitedly told my fellow hikers, and they either a) didn’t believe that they weren’t ants, or b) didn’t care much. :p

    • I can’t imagine having any interest in nature and NOT finding something like that really cool to see. I guess I’m always a little surprised when ‘naturalists’ aren’t interested in nature.

  8. harry zirlin says:

    Ted, I have only found this species twice (both last year at Ward Pound Ridge, Westchester Co. NY) Both times they were found sweeping dead and dying branches of mostly oaks and hickories. The specimens in NY were all jet black, not half red and half black like this one. Other ant-mimic Cerambycids apparently are often red in the south of their range and black in the north, pehaps reflecting that red ants are more common in the south.

    • Very interesting observation. Euderces picipes is well know for being all-black in the north and red-black in the south(west). I’d love to see some of those all-black Cyrtinus if you ever run into them again.

  9. Marlin says:

    One of my favorite ‘bycids; probably because it is so small. Saw my last living specimens 29 years ago on Crataegus outside of Wharton, Texas. They were abundant then and I beat maybe 30-40 from a single tree. Haven’t seen them in Iowa, even though I still have the search image when I scan my beating sheet. Nice to know they also occur at a northern latitude (southern NY). Maybe they can be found in Iowa. Thanks Ted for appreciating the smallest of longhorns.

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