Wasp/yellowjacket in mason bee house

Asked April 30, 2018, 2:40 AM EDT

I have a mason bee house in my backyard that we've been using for the past couple of years to help pollinate our fruit trees.

I went out this evening to peek in the house with a flashlight just to see what's going on, and I noticed this nasty looking critter (yellow-jacket?) and nest. I'm wondering if you can help me identify it from the attached photo, and if you have any advice as to how to get rid of it/them without harming my mason bees.

Multnomah County Oregon

1 Response

Thank you for including the image of the wasp and its nest inside the “housing” you provided for the mason bee tubes.

This insect is a European paper wasp (Polistes dominulus), an invasive insect that was first identified in the US in 1981.

Even though the yellow and black markings suggest it is a yellowjacket, but it is not.

One difference is in the antennae of these insects: Yellowjacket antennae are black where those of Polistes species are black with orange (or golden) tips. Another difference is the nest: Yellowjacket nests are large, enclosed structures whereas the nests of Polistes are small and open at the underside. (See images and info at “European Paper Wasp” - http://extension.colostate.edu/topic-areas/insects/european-paper-wasp-5-611/)

It’s likely this paper wasp won’t be a problem to the mason bees because bees are not on its diet. But you can avoid next year’s generation from nesting near the mason bees by doing 1 of 2 things: (1) Fill the cylinder totally with mason bee tubes, or (2) Stuff paper toweling to fill the space.

Even so, it’s worth knowing that Polistes is an aggressive species. It is very likely to sting you if you are within 20 feet. Repeatedly! In addition to that, multiple wasps often cooperate building these small nests. (http://www.pesticide.org/bees_wasps). They will die at the end of the year.