The “obscure” Dicerca

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Photo details (first 2 photos): Canon 100mm macro lens on a Canon EOS 50D, ISO 100, 1/250 sec, f/13, MT-24EX flash 1/4 power through diffuser caps

During my recent trip to northwestern Oklahoma, we visited Packsaddle Wildlife Management Area, a 17,000-acre chunk of land containing mixed-grass prairie, shinnery oak (Quercus havardii) shrublands, and mesic woodlands along the South Canadian River.  In one of these woodlands, I encountered a small grove of persimmon (Diospyros virginiana) trees – some of which had recently died.  Whenever I see dead persimmons, I immediately think of the jewel beetle species, Dicerca obscura (family Buprestidae).  This attractive species is one of the larger jewel beetles occurring in our country, and although it is fairly commonly encountered in collections, seeing the living beetles in the field is always a treat.  Dicerca obscura is most commonly associated with persimmon, from which I have reared it on several occasions, but Knull (1920) also recorded rearing it from staghorn sumac (Rhus typhina).

IMG_0534_1200x800I began inspecting the dead trees for the presence of the beetles but didn’t see any at first.  Then, I saw something moving right where I had been looking.  I had, in fact, looked right over this beetle without seeing it – even though I knew what could be there and what it looked like.  I don’t know if the species name (from the Latin obscurus, meaning indistinct) was actually given because of its marvelous cryptic abilities, but it certainly could have been.  As I continued to inspect the trees more closely, I found several additional adults – all sitting on trunks that I had just inspected a few minutes prior.  I couldn’t help but think of the irony – in collections, Dicerca beetles are quite gaudy and conspicuous appearing, with their shiny, brassy colors and exquisite surface sculpturing (as exemplified by Dicerca asperatathis photo of a pinned specimen in my collection of a similar species, D. asperata).  However, in the context of their environment, their coloration and sculpturing helps them blend in and become almost invisible.

Dicerca obscura occurs across the eastern U.S. but is absent from much of New England, the Appalachian Mountains, the Allegheny Plateau, and the upper Midwest – apparently due to the absence of persimmon in those regions.  It has been been recorded in Oklahoma as far west as Oklahoma City (Nelson 1975), so my record from Ellis Co. in far northwestern Oklahoma represents a bit of a range extension.  This is not surprising – the species will probably be found wherever persimmon grows.  You’ll just have to look carefully if you want to find it!

REFERENCES:

Knull, J. N.  1920.  Notes on Buprestidae with descriptions of new species.  Entomological News 31:4-12.

Nelson, G. H.  1975.  A revision of the genus Dicerca in North America (Coleoptera: Buprestidae).  Entomologische Arbeiten aus dem Museum G. Frey tutzing bei München 26: 87-180.

Copyright © Ted C. MacRae 2009

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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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10 Responses to The “obscure” Dicerca

  1. Joan says:

    You are so right Ted. Some of these insects can be easily overlooked because they blend in so well. I think also people like you and I see them easier because our eyes have adjusted and are on the lookout for these bugs but others will not find them quickly.

    • Hi Joan. Yes, even with our fine-tuned search images, this was a great example of how these things can still avoid detection. I guess we collectors can also be considered ‘predators’ of sorts🙂

  2. Clay Bolt says:

    Hey Ted,

    Great post. I am amazed by crypsis in nature and try to photograph species exhibiting this behavior whenever I can.

    Clay

  3. DougT says:

    Nice photos. It always amazes me when I first find something cryptic, and then quickly notice a bunch more right where I had already looked. The search image is a powerful thing.

    • Hi Doug. This happens to me all the time – precisely why I went back and re-examined some of the trunks I had already searched after finding the first one, even though I already knew what I was looking for the first time I inspected them.

  4. Marvin says:

    Thanks, Ted. I’ll have to check out my dead persimmons more closely.

  5. What marvelous camouflage. That’s one of our favorite experiences — when you look over a leaf, a landscape, or a tree’s bark, and only later realize that you missed something hiding right in front of you.

    • Hi K&R – we may try, but it’s impossible to see everything. Kind of along the same lines, it amazes me when I return to a place repeatedly and continue to find new things. It’s a huge, amazing world out there.

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