Beneficial or damaging insect

Asked April 18, 2020, 8:59 PM EDT

Underneath the eaves on the south side of our house, I found an insect that was in the grooves of T-111 siding. It appeared that the insect was storing food in catacombs that were a hard mud like material. Any idea what this was and is it harmful to the exterior of the home?

Washington County Oregon

1 Response

The insects are native mason bees, Osmia species, which take advantage of pre-existing holes. The individual cells in a hole contain a yellow pollen ball on which the female lays an egg. She then closes each cell with mud. The new adults will emerge next spring.

Mason bees are beneficial insects. They're among the first pollinating insects active in the spring. They are especially helpful for people who have fruit trees because these bees are active even when it rains.

You might be interested in this publication: "Nurturing Mason Bees in Your Backyard in Western Oregon" - https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9130.pdf