Beetles Under Bark of Dead Pine Trees
On November 8, 2015, I was back in the pine plantation behind the house. The plantation was thinned a few years ago, and the loggers left a fair number of smaller trees that had been cut down, but that they didn’t then haul away for whatever reason. By this time, they had rotted enough that the bark was loosening, and with very little effort the bark could be peeled off entirely. And, for just about every tree that I checked, there was at least one of these beetles:
Each of them had made a little hollow under the bark by scraping down to the wood, and pushing aside the debris to make a wall around themselves. They were obviously settled in to hibernate through the winter, depending on a nice blanked of snow to keep their downed log from freezing too hard.
These were reasonably good-sized beetles, about half an inch long, and had a consistent pattern of brown and black marks on their strongly-ridged wing covers.
They had pretty good eyes for a beetle, and while their mandibles were not negligible, they were not much more than one would expect for chewing up rotting wood.
They appear to be Ribbed Pine Borers, Rhagium inquisitor[1]. And, it turns out that this isn’t a case of adult beetles building a nest that they then hibernate in. The little pockets under the bark are made by the larvae, and then they pupate in the chamber, obviously turning into adults just before the snow falls. They then hibernate in the already-existing chamber, coming out in the spring.
Anyway, these are a type of flower longhorn, related to the several other flower longhorns that I’ve posted previously. They are also considered a forest pest. They get under the bark of weakened or damaged trees, and can spread fungal infections from tree to tree. And, as I was seeing, they can become very common when the conditions are right.
I did replace the bark over them when I was done, although I suppose the owners of the pine plantation would have probably preferred that I killed them outright. Not that three or four beetles would have made much difference to their population, there must have been thousands of them.
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[1] That name, “inquisitor”, sounds kind of sinister. “Nobody expects the beetle inquisition!”
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