An irresistible sight!

One of the few highlights of my Memorial Day weekend collecting trip came in the earliest moments of my visit to Ha Ha Tonka State Park.  My destination was Ha Ha Tonka Savanna Natural Area, and a short walk through fire-restored woodland led me to the open glade where just a few years earlier a UMC student had collected the rare and little-known Agrilus impexus.  Entering the glade, I was all set to begin sweeping the vegetation along the woodland/glade interface, paying special attention to any honey locust (Gleditsia triacanthos) that I might happen to find in the area as a potential host for the beetle.  What I saw instead as the glade opened up in front of me was a sight that any collector of wood-boring beetles will find almost irresistable – a recent wind-throw!  In this case, it was a black oak (Quercus velutina) laying in full sun – its bright brown leaves suggesting that it had fallen within the past few weeks (and would thus still be emitting the volatiles that wood-boring beetles find so attractive).  I wanted to begin looking for A. impexus, but I knew there would be beetles actively crawling on the trunk and branches of that tree.  I couldn’t resist it – I dropped my sweep net and beating sheet and made my way to the tree (in the end it didn’t matter, since no other beetles – including A. impexus – would be seen that day).

I already had an idea what I might find.  Recent wind-throws are the domain of Chrysobothris, and if the tree is a deciduous species then this means members of the Chrysobothris femorata species-group.  I recently featured one of six newly described members (C. caddo) of this taxonomically challenging group (Wellso and Manley 2007), providing a synopsis of the now twelve species in the group and their primarily host preferences.  Fully half of these are associated primarily or exclusively with oaks - four occurring in Missouri (quadriimpressarugosiceps, shawnee, and viridiceps).  Of these, C. quadriimpressa is the most commonly encountered (although the others are by no means uncommon), and all of the nearly dozen or so beetles I found on this particular tree in fact represented that species. Confirmation of my ID would require microscopic examination of the female pygidium (which is shallowly impressed on each side of the middle) and male genitalia, but in general this species can be distinguished in the field by its smallish size (~10-12 mm in length – rugosiceps and shawnee tend to be larger) and the post-median pair of foveae (circular impressions) on the elytra being joined (they are distinctly separated in viridiceps).

As we’ve seen with other species of jewel beetles (e.g., C. caddo, Dicerca lurida, D. obscura), adults of C. quadriimpressa are incredibly cryptic and nearly impossible to see on the bark of their hosts – at least until they move.  They are notoriously difficult to approach – their large eyes and penchant for rapid escape flights suggesting excellent vision.  This is a useful capability for insects that must expose themselves to would-be predators (and beetle collectors) during daylight hours while actively searching dead trees for mates and oviposition sites.  One thing I can’t figure out, however, is the role of the intensely blue feet in this and other cryptically colored Chrysobothris species (see also C. caddo).  Any ideas?

Photo Details (insect): Canon 50D (ISO 100, 1/250 sec, f/16), Canon 100mm macro lens w/ Kenco extension tubes (68mm), Canon MT-24EX flash (1/4 ratio) w/ Sto-Fen diffusers.  Post-processing: levels, unsharp mask, minimal cropping.

REFERENCES:

Wellso, S. G. and G. V. Manley. 2007. A revision of the Chrysobothris femorata (Olivier, 1790) species group from North America, north of Mexico (Coleoptera: Buprestidae). Zootaxa 1652:1–26 (first page only).

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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19 Responses to An irresistible sight!

  1. I am continually reminded why you named the beetle carnival “An Inordinate Fondness.” This beetle is so exquisite. Have no idea about the blue feet (of course I don’t, I’m no entomologist), but I like them. Reminds me of the Blue-footed Booby (bird), whose blue feet are quite the attention-grabber.

    If these beetles run away when approached, how did you get such a fantastic picture? Wonderful! And thanks for the layman’s language about how you knew to look at this fallen tree for beetles…will come in handy for me since I’ve never really known how to look for beetles in particular. (Besides peeling back bark)

    • Thanks, Amber. I get these pictures by: 1) anticipating the situations where I am likely to see them, 2) approaching the tree extremely cautiously so that I can see them before they are alarmed, 3) approaching even more cautiously once I do see one, 4) settling into what I think will be a stable position for the shots while it is still ~3-5 feet away, 5) getting the beetle in the viewfinder and slowly dialing in on it until I’m close enough, and 6) hoping that the beetle will settle down long enough for me to fire off a few frames before it moves again. ;)

      I shoot a lot of frames – half are deleted immediately in the field, half of the remainder get deleted when I see them on the computer, and half of what’s left might get post-processed and show up here. I try to get your basic dorsal shot right away (like the one shown here) and then work it from different angles to get better views of different characters. I’m not always successful in getting the latter (this being one of those times).

      • I see…not all that different from photographing a bird. Birds often bolt at the sound of the shutter clicking. Hmmm, makes me wonder, do beetles hear well? Never even thought to ask/look it up.

        • Beetles do not have true ears like many other insects (grasshoppers, cicadas, etc.). However, they do feel vibrations, and these beetles in particular often communicate by “tapping” their abdomen against the wood. I do see them “react” to the shutter click sometimes, but I’ve always assumed it was the flash rather than the sound that caused this.

  2. jason says:

    The blue feet are simple, Ted. Any creature who takes pride in its appearance wants at least a hint of color.

    I didn’t have to see beyond the first photo to understand the title of this post. I knew precisely what you meant. And the beetle is a good find. Great photo of a very handsome insect.

    • Thank you, Jason. I tried getting some good close-ups of the face (which is bright green in males) but just couldn’t get a good angle on them as they scooted around on the log. I suppose I could’ve kept one alive and done it in the lab afterwards, but myeh…

  3. Paul says:

    Many of the Buprestids I’m collecting have brightly colored legs and feet. Looking at them under magnification, head-on, the colors really jump out at you in such a way that I believe they may be used as intimidation to rivals or attraction to mates. Either that, or it is a way for the species to distinguish themselves from each other. At least that is what I have been thinking…

    • You might be onto something here, although it is primarily the facial coloration that seems to be sexually dichromatic (males have a bright green frons, while in females it is bronze). Both sexes have the bright blue feet, and not just in this species but also many others in the genus.

      I’ve wondered if they might function in a similar manner to the blue tails found in many lizards, i.e. diverting the attention of a potential predator to an “expendable” part of the body (giving the beetle a chance to escape and hobble another day).

  4. James C. Trager says:

    While handling a leopard moth yesterday, I noted iridescent blue legs. Never saw that before, as I’ve always seen them at black lights. But I have no idea what those do either. The abdomen of almost the same blue with conspicuous orange spots certainly looked inedible, though. Any idea as to the palatabilty of these beetles?

  5. dragonflywoman says:

    Lovely photo Ted! I don’t get to see too many buprestids, but I love them. Such elegant beetles!

  6. peteryeeles says:

    Could the blue be linked with UV reflectance? I believe certain butterflies (eg, Hypolimnas bolina) use UV reflectance in sexual selection, and although both look blue to our eyes (in some species), males are more brilliant under UV.

    Doesn’t answer why they are blue (unless males reflect more UV), but it might be interesting to see anyway!

  7. TGIQ says:

    Gorgeous critter! Those blue feet really jump out at you…I was going to suggest the blue-lizard-tail analogy, but I see someone’s brought that idea up already. I for one appreciate your drive to get “the shot” and the patience that requires…

    • Thanks, TGIQ. I have noticed I’m collecting far fewer specimens these days with so much effort going into the photography. That’s okay – I’ve got so many bugs I don’t know what to do with them all :)

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