There’s an attractive, mid-sized black wasp out and about this time of year that has a unique home-making habit. Meet the grass-carrying wasp, Isodontia mexicana.

Grass-carrying wasps are in the Sphecidae family of thread-waisted wasps, and as you can see the waist is not only narrow but also long. Isodontia mexicana have a reddish-brown spot on the waist near the abdomen. For those who enjoy a new vocabulary word—that thread waist is called a “petiole.” 

Females of these non-aggressive wasps provision the nest with paralyzed tree crickets (mostly), or katydids and lay an egg on or near each insect. They stuff in grass to cushion and separate each offspring. In the wild, they build nests above ground in the hollows of wood or other crevices. In the non-wild, grass-carrying wasps often build nests in cozy manmade spaces like the gaps between storm windows or even inside wind chimes!

Although they don’t leave pollen in the nest for their young, the adults do act as pollinators, because they visit flowers to eat nectar themselves. I’ve not seen a grass-carrying wasp in the act of carrying grass, or carrying prey, but there are pictures online if you care to search—it’s an impressive load for the three-quarter-inch wasp to transport.

Stay curious!

See more of Karen’s work here.


Column with interesting comments on where nests have been found: Accessed 9/21/22. 

Article by Heather Holm, with a photo of a stocked nest: Accessed 9/21/22.