San Antonio Natural Area Parks
News & Articles

Beetle damage in the inner bark of a fallen tree.

No, we're not discussing a collection of photographs of those British rock stars. These galleries are networks of tunnels carved by beetles beneath the bark of trees.

Perhaps you have noticed these tunnels (like those shown in the photograph) on dead standing trees (snags) or fallen trees; they look like someone has been carving hieroglyphics in the wood. This is the work of a bark beetle. There are over 600 beetles in the family Scolytidae that are commonly referred to as bark beetles.

Adult bark beetles bore through bark to the cambium layer of suitable host trees. Females excavate a tunnel between the bark and wood along which they lay their eggs. Upon hatching, each grub burrows away from the egg tunnel and feeds on the live bark tissue (phloem) and outer cell layers of wood (xylem). This results in multiple, thin, parallel tunnels like spider legs running perpendicular to the main

tunnel. When the trees die, as the bark sloughs off, the intricate work of the beetles is revealed.

As a general rule, bark beetles attack trees that are weakened or dying due to stress factors such as drought, disease, smog, mechanical injury, or alteration of the water table and root damage due to nearby construction. They are also attracted to recently cut wood that still has bark. If you haven't noticed beetle galleries before, take a look for them now on snags and fallen logs where the bark has fallen away.

Peggy Spring is Park Naturalist for Natural Area Parks education and volunteers.

design by woodland company | sponsored by Friends of Friedrich Park