Meet the Grass-Carrying Wasp: Gentle Pollinator, Cricket Hunter, Nest Architect

Unlike ground-nesting relatives, the grass-carrying wasp (Isodontia mexicana) chooses aboveground cavities — hollow stems, holes in wood, even window screens. These gentle, solitary wasps visit summer flowers, hunt tree crickets, and line nests with grass blades. Provide stems and forage plants, and they'll move in.

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Quick Facts

• Family: Sphecidae (thread-waisted wasps)
• Latin name: Isodontia mexicana
• Range: N. America east of Rockies, S. Canada to Central America
• Habitat: Woodland edges, gardens, meadows, prairies, old fields, farms; nests in screens/window gaps
• When to see: Adults early July (earlier south); nest building July; flower visits mid-July–early Sept

Adult on rattlesnake master. Holm Design & Consulting LLC

Ecological Role

Females hunt tree crickets (Oecanthus spp.) — herbivores that damage plants. Adults nectar on flowers, preferring white blooms, and pollinate in the process. Energy from nectar fuels nest provisioning.

Female with wood mulch fiber for nest division. Holm Design & Consulting LLC

Identification

• Adults: ~0.7" (18 mm). Black head/thorax/abdomen. Thread waist. Medium brown wings with blue iridescence. Thorax covered in fine white hairs.
• Larvae: Cream, legless, develop in cavity on cached crickets.

Nest cross-section: crickets (green), cocoon, grass partitions. Holm Design & Consulting LLC

How to Attract Them

1. Provide Nest Sites

Cut hollow stems to 10", bundle horizontally with burlap twine or in open-ended container. Place aboveground in spring. Seal unwanted gaps (e.g., storm windows) to deter nesting there.

2. Go Pesticide-Free

Especially on flowering plants.

On common boneset. Holm Design & Consulting LLC

3. Plant Forage & Supply Grass

Nest initiation mid-July. Females cut grass blades, carry them mandible-held, coil into partitions/plugs. Often seen flying with grass.

Preferred nectar plants:

• Summer: American spikenard (Aralia racemosa), common boneset (Eupatorium perfoliatum), Virginia mountain mint (Pycnanthemum virginianum), rattlesnake master (Eryngium yuccifolium)
• Late summer/fall: Goldenrod (Solidago spp.)

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Life Cycle

Females mate, select aboveground cavity (rarely ground holes). Create grass-partitioned brood cells or communal chamber. Hunt crickets high in canopy, sting to paralyze, carry back. Lay egg on provisioned prey. 1–2 generations/year in upper Midwest/Northeast. Larvae eat crickets 4–7 days, spin cocoon, overwinter as prepupae/pupae. Complete development spring; emerge as adults in July.

On stiff goldenrod. Holm Design & Consulting LLC