Home Sweet Home for Grubs

So we got around to splitting the wood, a pile of various types of logs we've been collecting for a few years.  It's a fair piece of work but gives the householder such a warm feeling once that wood is all split, sized and stacked to cure in the summer sun.  Also, the beauty of the wood as each smaller log or huge stump is split to reveal its unique coloration, texture and odor makes the job a joy.  Not to mention the satisfying crack as a log splits apart under the brute force of the hydraulic splitter.  You didn't think we used an axe, did you?

Then I got a special treat when this grub tumbled out of a split white alder log.

This is Dicerca hornii, a metallic wood boring beetle that specializes in alder, prunus and other deciduous trees.  In the wood-destroying organisms trade it is referred to somewhat generically as a flathead borer.

You can see the flattened oval shape of the grub's tunnel in the alder log from whence it came.

There are several tunnel holes that were exposed by the split in this log, maybe from other grubs still hidden inside the wood or maybe this grubs extensive tunnel.  D. hornii female beetles lay eggs on failing trees or standing dead trees, and the grubs feed on the wood creating tunnels through the wood as they grow.

Same log, surface under the bark shows no tunnels or galleries and leads me to believe this beetle species does not feed on the cambium directly under the tree bark.















I think it takes about a year for the grubs to mature into the colorful adults also known as jewel beetles.  These photos are from a few years ago in December when I saw my first jewel beetle.

When the beetle takes flight, the lifted elytra reveal an emerald green abdomen as an extra treat for the observers of this interesting species.