What's this bug?

Asked September 28, 2017, 6:02 PM EDT

We have had a sustained population of these bugs here in Santa Clara (Eugene) all summer. They are into everything. Any idea what they are; and what they do for a living? Thanks.

Lane County Oregon household pests insect identification elm seed bugs

4 Responses

Thank you for uploading the images with your inquiry. Your unwanted visitors are invasive elm seed bugs, Arocatus melanocephalus. These insects were first identified in Oregon about 10 years ago.

Elm seed bugs are one of several similar nuisance insects which gather on the warm side of the house during fall, and then migrate indoors through small cracks and crevices. Sometimes, as in your case, they also invade buildings to escape summertime heat.

The best management is to avoid pesticides of any kind (they're unlikely to help) and to block their entry. In general, that means to seal all indoor cracks and crevices where they might be entering (but wait until July to plug/seal cracks outdoors). A household vacuum can help limit their numbers indoors or, if they're especially numerous, use a wet-dry shop vac.

See "Managing Elm Seed Bugs Around Your Home" (http://www.cals.uidaho.edu/edcomm/pdf/CIS/CIS1223.pdf).

Thanks. After I wrote to you, I stumbled upon this website where a photo I took of our bugs (attached) seemed to match perfectly with this site's ID of the bug as a mediterranean seed bug. Are they possibly one in the same? <https://www.whatsthatbug.com/2016/03/31/mediterranean-seed-bug-washington/>
(I meant to include this photo before, but sent two of the key pad by mistake.)

No, they’re not. I think yours are Rhyparochromus vulgaris, another of the dirt-colored seed bugs. (My first thought went to the elm seed bugs because they’re known to migrate indoors during heat waves.) See “New Pest Alert and Update; Introduced Exotic Seed-Bugs are New and Increasing Nuisance Problems . . .“ (https://agr.wa.gov/PlantsInsects/insectpests/Exotics/Surveys/seedbugs_06.pdf).

In any event, the management for all these invasive seed bugs is the same as described above. All are considered important nuisance insects because they overwinter on and in structures. Several other seed bugs with the same habits are Raglius alboacuminata and several Arhyssus species.

If you would like a first-hand ID, take samples to the Lane County Extension Service office, 996 Jefferson Street, Eugene, OR; corner of 10th Ave. & Jefferson Street. Hours: Monday - Thursday 10:00 am to 1:00 pm & 2:00 pm to 5:00 pm; closed Friday – Sunday.

Thanks for all your help.