A Little Bit More
The illustration on the unit poster focuses on only one species of borer but there are many in North America. When you run down the list of tree species that are vulnerable to borers, you quickly realize that there aren’t many that can avoid their invasion. The term “borer” describes two major beetle families (Metallic Wood-boring Beetles and Long-horned Beetles) that attack trees. Many species only invade certain kinds of trees (females taste a tree before laying eggs to ensure the “correct” location for their eggs) but some borers are more general in their preferences and may feed on a wide range of tree and shrub species.
On warm spring days, adult Metallic Wood Borers may be found actively crawling around on tree trunks in full sun but are quick to take wing if approached. Eggs are laid in bark crevices or injuries, then hatching young tunnel into the inner bark and begin feeding. Over the course of a summer, the larvae grow quickly and can girdle a branch with their meandering galleries. Borer tunnels typically are filled with frass (sawdust-like material) and are different in appearance from those made by ants or termites. Once the larvae are full-grown, they tunnel into the sapwood and rest as pupae in a chamber they’ve excavated. After a week or so they’ve changed into adults, and chew their way out of the tree leaving an oval emergence hole behind in the trunk. A few borers living within a tree are not a problem but if the number is high enough, it can cause a tree to weaken and even die.
In the past when the American Chestnut was hit by a blight, weakened trees all across the Northeast were especially attractive to borers. Today we see the results of the borer invasion in our “wormy chestnut” furniture.
Activities
Science – Lemons to Lemonade
Objectives: See an example of a liability turned into asset
Materials: access to internet
Have you ever seen wormy chestnut or maple for sale in antique shops? Well, those weren’t “worms” that made those holes, they were borers. There are many different kinds of borers living in North America so the Flatheaded Appletree Borer we focused on in the unit is probably a different species than the one making the “worm” holes in chestnut or maple. It’s interesting to note that initially, American Chestnut lumber was regarded as unfit for use when it was full of holes. However, as this species fell prey to the fungus all across the Northeast, quality chestnut lumber was more and more difficult to obtain and those trees that were available, were being riddled with holes from borers. Some marketing genius had the bright idea of marketing an “inferior” grade of chestnut wood into what we know as “wormy chestnut”. His strategy worked and soon the once inferior wormy wood was being purchased in preference to the normal, clear lumber – go figure!
Take a look at these two sites to learn more about how the lumber industry took a liability (wormy wood) and turned it into an asset.
Wormy Chestnut Story
View Wormy Chestnut
Key Concepts
Structures and Functions, Life Cycles, Identification, Growth and Development
Questions
Do you have a question for a naturalist? Go ahead and ask!
It's easy -- just fill out this form, submit your question and you'll receive an answer shortly.
Posted by Dawn Lutrell on May 16, 2006 at 03:04 PM
Q: I often see what I have heard refered to as Insect "Galleries" on exposed wood - under the bark areas of trees.Are these "lines" actually caused by insects and what other insects besides Bark Beetles would cause these markings?
dawn
A: There are several kinds of beetles that live within both dead and living trees but the ones that are most likely to be what you've seen making the shallow tunnels are the bark or engraver beetles (family Scolytidae). These are small beetles, not much more than 6-8mm in length, that live just beneath the bark. Both the adults and larvae mine galleries beneath the bark and the system of tunnels they produce may be quite extensive. These beetles tend to be rather species specific (focus on a particular species) and can do more or less damage, depending on their population levels. Hope this helps you out. Thanks for asking.