Wednesday, November 14, 2007

Mystery Twig

Over the last month, we have found numerous branches like the one shown in the first image. We have been mystified by what may be the cause of the unusual cut discovered at the end of the branch (next two images). We added it to our list of "Things We Must Find Out If We Are To Continue Calling Ourselves Naturalists." However, we had not yet investigated the issue as it remained low on the larger list of "Things We Must Do To Keep The Center Operating."

You do not need to leave your room.
Remain sitting at your table and listen.
Do not even listen, simply wait.
Do not even wait, be still and solitary.
The world will freely offer itself to you
To be unmasked, it has no choice.
It will roll in ecstasy at your feet.
- Frantz Kafka

Well, if putting the issue on the back burner is the same as remaining "still and solitary," then that's what we did. The answer did not "roll in ecstasy" at our feet...rather it arrived in the large form of Tony Mills, education director at the Lowcountry Institute. Tony was one of the instructors during Monday's master naturalist field trip and he found a similar branch on the bluff above Mallard Lake. He enlightened us by describing the twig girdling work done by the female longhorned beetles of the family Cerambycidae.

In September through October, the female beetle lays an egg below the bark of a live twig between 1/4" - 1/2" in diameter. The last image shows the striations where the eggs have been deposited. Once the female is finished depositing her eggs, she will chew most of the way through the twig. The final image shows the girdled twig with only the center portion left unchewed. The twig will eventually die and fall to the ground. The eggs will remain in the twig until the following August when they will hatch. The larvae will feed and pupate within the twig and then emerge as an adult to begin the process anew. Only one generation occurs each year.

The damage to the trees is usually minimal, though the extra leaf and twig debris in the yard might not be appreciated by the yard-clearing child labor force.

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