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Thursday, December 25, 2008

A Shiny New Beetle

Two weeks ago it still seemed like a California dream winter with sunny days in the mid-70s and slightly crisp but hardly cold nights. We knew of course this would come to an end soon enough and so set about to split the wood. We've had a couple cords worth of alder logs curing in the yard for about 2 years and the time was right to split and stack them for burning season. We heat with wood in an EPA-approved stove with reduced particulate emissions for about 6 weeks per year; we won't use anywhere near all that wood this winter but it makes us feel rich looking at the neat pile of perfectly sized logs ready to burn.

After the wood was split, I was poking around a pile of bark chips and random not-yet-stacked logs when I noticed this interesting critter. It's a buprestid beetle: a metallic wood boring beetle probably of the genus Dicerca. There's not too much specific information on these, but I believe the larvae consume and live within dead wood for at least a year. The University of Riverside feels this genus is not particularly troublesome to human interests in that they eat dead wood. Don't know what the adult beetles feed on; I saw one photo of something similar visiting a flower. I'm also not sure whether the adults just happened to eclose as the logs were being moved and split, if the disturbance prompted them to emerge, if the adults were in the neighborhood and had been attracted to the scent of the freshly split wood, or if the adult beetles actually spend time after maturing within the wood. Lots more to observe about these guys.

They were fairly active and kind of weird looking with those bee-like faces, peculiar pointed elytra and coppery sheen. One of them opened its wings to fly, revealing a bright green dorsal surface of its abdomen. What's the function of that?

Now the real weather has set in and we're heating with wood and possibly beetles. That chunk of wood pictured below wasn't our yule log and I'm not sure yet whether those holes in it were created by carpenter bees (Xylocopa varipunctata) or Dicerca beetles. I'm guessing the bees. and it's nice to know we have so effortlessly provided a wealth of resources for other creatures.

1 comment:

Anonymous said...

I believe this is a species in the related genus Poecilonota, probably either P. californica or P. salixi which are known to breed in willow and poplar (same plant family as alder). They are strictly dead wood breeders, so they don't have any real economic importance.

The brilliant blue coloration on top of the abdomen is something a lot of buprestid beetles exhibit. It could be "flash coloration" intended to confuse pursuing predators (i.e. birds).

Nice series of pics.