Subject: What kind of nest is this
Location: Hudson, NH
February 15, 2014 12:33 pm
I found these today in the slots in my window were my screen would go. I only have half screens so the top never has anything in it.
Signature: Angela

Nest of a Grass Carrying Wasp

Nest of a Grass Carrying Wasp

Dear Angela,
We believe this is the nest of a Grass Carrying Wasp in the genus
Isodontia.  According to BugGuide:  “Females make nests in a tree, hollow stem or other cavity, divide into sections and close with grass. They provision with Orthoptera (Tettigoniidae, Gryllidae)” and “These wasps commonly make their nest in the narrow track found above outer windows.”  We cannot tell if the nest in your photo has been provisioned with Crickets.  The female Grass Carrying Wasp paralyzes the cricket which remains immobile, but alive, as the wasp larva feeds upon it.

Update and Question:  April 18, 2014
Subject: Grass-carrying wasp
April 17, 2014 1:32 pm
When in the spring/summer is best to clean out old grass carrying wasp nests allowing them to emerge as happy, healthy adults?
Signature: Dee Maack

Nice question Dee.  This is speculation on our part.  Based on information on Grass Carrying Wasps that is available on BugGuide:  “Taken from the Internet Reference below (Penn State): The adult wasps emerge from their cocoons in early summer, mate, and the females locate a suitable nest site. She collects blades of grass and grass and hay stems to line the nest cavity. The wasp can be seen flying through the air with the blades trailing beneath her. She lands at the hole and enters, pulling the blade in behind her. After the nest is prepared, she hunts for tree crickets (i.e., Oecanthus sp.), captures and paralyses them with her sting, and transports them to the nest. She deposits eggs in the nest and the emerging larvae will feed on the living, but immobile crickets. When the larvae reach the appropriate size (in 4–6 days at 70–75° F.), they spin a cocoon and pupate. The adult wasps emerge in 2–3 weeks. In Pennsylvania, Isodontia mexicana typically produce two generations per year.”  We would suggest mid to late June as a time to consider clearing out nests from the previous year, however, if you notice pupae as you are cleaning out the windows, you may want to delay the clearance a few more weeks.  We have added your question to a recent posting on the nests of Grass Carrying Wasps.

Location: Hudson, New Hampshire

One Response to Probably Grass Carrying Wasp Nest

  1. Mike Melkonian says:

    We get what looks like these wasp nests but they are BEHIND the screeen. I don’t see any larvae but have this in about five windows. Maybe it’s just the start. I can’t post a pic here so maybe I’ll start a new thread.

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