Thursday, September 30, 2010

Invasive Species Under Your Nose - European Earwig

Do you stop to smell the roses? If you do, you’ve no doubt met a common invasive insect, the European earwig. They love to hide in roses and other nooks and crannies that offer shelter and high humidity.  At my house they like my hose reel.  I even saw some on the roof recently while I was cleaning off moss.

There are no native earwigs in Oregon; if you see one, it’s an invader.  By far the most common is the European earwig, Forficula auricularia L.  Earwigs are omnivores, occasionally becoming minor pests.  Mostly they are just a nuisance or to the entomologically inclined, a curiosity.

I’ve had a soft spot for earwigs since encountering very large maritime earwigs while processing seaweed in a previous job on the East Coast.  Like all earwigs, they have prominent cerci (forceps) at their tail end. Interestingly in this species, the cerci are curved and asymmetrical in the male and straight in the female.

Cerci, used for mating and defense, are not the only odd thing about earwigs.  Here is some more earwig trivia: Unlike other insects, the mothers stick around and protect their young after they hatch.  Though they appear wingless, many species can fly; their wings are folded up under small wing covers on their thorax.  Earwigs are an ancient group; they were crawling around under the noses of dinosaurs.

Oregon has a very interesting history with earwigs.  In the 1920s and 1930s, Oregon State Agricultural Experiment Station, State Board of Horticulture, Bureau of Entomology, City of Portland, and Multnomah County cooperated on earwig surveys and releases of biological control agents.  For a while, Portland even had a City Earwig Commissioner!

Here is an excerpt from a 1930 report: “A brief survey was made to determine if European earwigs were present in all parts of Portland, except in the main business district.  This survey was conducted by placing tar paper bands on trees and the relative number of earwigs found under each tar paper band was noted.  It was found that earwigs were present in every section of the city in large numbers.”1

It would be interesting to repeat the survey now.  Perhaps the parasites introduced way back then are the reason European earwigs are not a serious problem now.  To my knowledge, no one has followed up in the 90 years since.  Anyone know a student in search of an interesting science project?

Another interesting project would be to survey for the maritime earwig.  They have been introduced and become established in both California and British Columbia.  If they aren’t in Oregon yet, they probably will be soon.  Keep your eyes open next time you’re at the coast, you could be the first to report this exotic species!

Earwigs are an example of an invasive species right under your nose, but don’t worry about them crawling in your ears – that’s an old wives tale!

Dan Hilburn

1D.C. Mote.  1931. The Introduction of the Tachinid Parasites of the European Earwig in Oregon.  J. Econ. Ent. 24: 948-956.

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