Thursday, February 10, 2011

Phloeodes diabolicus

Ironclad beetles are the tanks of the insect world. They are famous (or infamous) for walking away after being stepped on. There are even reports of species being run over by cars without apparent harm. To an entomologist, they are notorious for the challenge of getting an insect pin through their thick skin (cuticle). What usually happens is the first attempt bends the pin. The second attempt bruises the thumb and forefinger to the bone. And then with a combination of anger and grit (and with two hands gripping the shaft) the pin is forced through the reinforced exoskeleton. With luck it has gone through straight and without popping the legs off on the other side. Very often it doesn't - as verified by any number of oddly pinned specimens stuck to the bottom of unit trays in the museums of the world.

These images are of our most common ironclad beetle in the Central Valley - the diabolical ironclad beetle. How the species got its name is a mystery to me. Perhaps the shiny golden setae on a dark black background in many of the individuals reminded the author (LeConte) of fire and brimstone. Whatever the reason, it is a name (and a species) not easily forgotten.

These images were taken a couple of weeks ago near the King's River outside of Sanger (California). I found a grove of old oaks with one fallen individual cut into bathtub-sized sections. The beetles were congregated under the thick loose bark. They are about three quarters of an inch long and feign death when disturbed - making them easier to photograph. Some of the individuals are completely black and all of them have small velvety black sections on their back. The golden white setae on the shoulders and elytral apex are also very striking - especially under magnification. In the past, entomologists have thought these color differences represented different species. This is hard to maintain when individuals of both patterns are found in the same place (even on the same log as I found here). A full study of this group of ironclad beetles has recently been done by Ian Foley and Mike Ivie (at Montana State University, and published in Zootaxa, 2008). They document a geographical change in this pattern (a cline) and have confirmed that the variability represents only one species.

The habitat shot is along Byrd Slough where I found the little devils.


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whatWAITNUUU said...

That's 2 of us then.

Anonymous said...

And me

Anonymous said...

and one more. I thought they were south america, not fresno?

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