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An Unusual Insect Found in Minnesota: Drywood Termites

Jeffrey Hahn, Asst. Extension Entomologist

Termites are present in Minnesota but they are not common. They are found in southern Minnesota up to about the Twin Cities area and very rarely discovered, if ever, in central and northern Minnesota. Minnesota's native termites are subterranean termites, Reticulitermes spp. They maintain colonies in the ground and attack wood that is contact with the soil. You rarely see the termites themselves because the bulk of them stay inside the colony while those that travel outside of it move about in mud tubes they construct so they can maintain the proper temperature and humidity they need to survive.

That is why the discovery of winged termites in a home in Minneapolis during September was so interesting and unusual. First, when termites swarm, i.e. winged forms leave the nest en masse, they do so in the spring (and this is very rarely seen in Minnesota). Even more interesting was when the termites were examined more closely, they were identified not as the local subterranean termites but as drywood termites. This group of termites is not native to Minnesota but is most commonly found along the costal areas of the southern U.S. from North Carolina to California.

Jeff Hahn

Photo 1: Drywood termite queen

At first, just a single winged termite was found at a window at this home. Shortly after that, about 100 were found behind a couch. In the next couple of weeks, dozens more were found either behind or under the couch. The resident had owned this piece of furniture for 14 years. She had purchased it in Minnesota and never lived outside of the upper Midwest with it. The resident had never received any items mailed from areas where drywood termites are native nor had she ever noticed termites or sawdust in her home before, especially around the couch.

This brought up several excellent questions: where did the termites come from; how long have they been in the couch; and have they spread into other areas of the house? Information about drywood termite biology helped to answer these questions.

Although the couch had never traveled to any drywood termite endemic areas after the homeowner bought it, it undoubtedly was built and/or stored in a warehouse somewhere in the south where these termites are native. It was there that the couch became infested. You wouldn't normally think that insects could infest a piece of furniture for 14 years without their presence being noticed but drywood termite colonies grow very slowly and it isn't unusual for them to take that long before they are mature enough to produce new queens. So it is extremely likely that the termites were in the couch when it was bought and had been in the furniture during that entire time the resident owned it. Because the termites were confined to the couch, they did not spread to other areas in the house.

Fortunately for the homeowner, the only necessary control was to remove the couch from her home. It was taken away by a local pest management company, heat treated to kill the termites, and then properly disposed of. All's well that ends well.
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