Mason Wasps

Subject: Wood boring….wasp?
Location: 48108 Ann Arbor, MI
June 3, 2016 10:05 pm
Hello! These guys are making a condominium in my barn. What are they? I am in zone 6b SE Michigan.
Signature: Mary

Mason Wasp drilling nest
Mason Wasp drilling nest

Dear Mary,
We embarked on a relatively lengthy internet search in an attempt to identify your Mason Wasp in the Subfamily Eumeninae, beginning with unsuccessfully scanning through all the genera on BugGuide.  According to BugGuide:  “Most species nest in pre-existing cavities (e.g., old borings in wood, hollow stems, crevices in rocks). They are called mason wasps because they use mud (or less commonly sand) as partitions between their brood cells. Some species construct nests in the ground.”  We then found this great site, Bug of the Week run by Michael J Raupp, Ph.D. that has a wonderful posting of Mason Wasps using pre-existing cavities.  At last we found a very similar looking individual identified as being in the genus
Symmorphus on Bug Eric, the awesome site run by Eric Eaton.  An image on BugGuide of Symmorphus canadensis looks very close to your species, but there is no indication that the females will excavate a nest if they cannot locate a pre-existing cavity.  We will contact Eric Eaton to get his opinion.  We suppose these beams may have been infested with some other boring insect and the holes were quickly appropriated by the Mason Wasps.

Mason Wasp Nests
Mason Wasp Nests

Oh thank you!
There’s a lot of them. They go into the holes, also.

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