Bark Beetle Designs

Buffy and I walked down into the ravine and crossed the creek on my property. Rain during the night left the water in the creek slightly cloudy. A Carolina chickadee gave its “chick-a-dee-dee-dee call,” and a rufous-sided towhee repeated “wheep.”

The light was right for a change, and I could photograph the bark beetle designs on this log. Bark beetles are 1/8 inch long, and all of them feed on the layer of wood between the bark and trunk of live trees. Usually they pick trees that aren’t the healthiest.

Different bark beetle species create different tunneling patterns. Look closely at the base of all the tunneling to the wider horizontal tunnel (which would have been vertical when the tree was still alive). A female made the tunnel and then laid her eggs in niches along the side. I assumed she probably laid eggs on both sides of the tunnel, but I couldn’t tell for sure because it was on the underside of the log. It may be hard to see in the picture that there are teeny parallel tunnels coming up from the main tunnel. The tunnels grew bigger as the larvae grew. When they matured, each made an enlarged space to pupate in. The adults emerge from their pupal stage in the spring and then bore out through the bark. From there, they fly to new trees and start the cycle again. There can be 1 or 2 broods a year. Long tunnels of the same width are made by adult beetles.

 This second picture shows the tunneling pattern of a different bark beetle species. It better shows how the larvae fed out from the main tunnel. These tunnels weren’t nearly as long  as the ones above. Bark beetles use both deciduous and coniferous trees. These can be found in mature woods with downed trees.

Downed trees, in various degrees of decay, can be quite fascinating.


2 responses to this post.

  1. Posted by Anna on March 10, 2012 at 7:19 am

    Cool! I’ve never seen such a thing! 😀


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