Meet the Pollinators: Double-banded Scoliid Wasp

Scolia bicincta, autumnal visitor of your pollinator garden

Photo by Catherine Serreau Thompson

By Catherine Serreau Thompson, Master Gardener volunteer

I glide in upon a gentle cooling of the air, when sunlight slants gold and asters open like late violets. My wings flash with hints of blue, my body dark and hairy, girded with two pale bands — a signature I bear as bicincta, “twice-girdled.” I am Scolia bicincta, the double-banded scoliid wasp, a creature of both flower and earth.

You may glimpse me alighting on goldenrod, milkweed, or thoroughwort; I sip nectar, brushing blooms with pollen on my fuzzy frame. Though I lack the social architecture of bees, I serve your garden quietly, a solitary bridge between blossom and seed.

My family has been drawn into stranger pacts: orchids that smell of us lure our males into false embrace, tricking them into carrying pollen. In such bargains, life deceives to persist.

Yet my secret life lies hidden in the soil. There, beneath your feet, plump white grubs of scarab beetles chew unseen roots. With bristled legs I dig toward them, guided by scent and patience. A swift sting stills the grub; I lay a single egg upon its body, a cradle and a tomb entwined.

I parasitize scarab beetle larvae (white grubs). By this strategy, I join the broader ranks of scoliid wasps long studied for pest control — in sugar cane, turf, or Japanese beetle suppression — though not always with perfect success.

My offspring will wake to feast on what once fed upon your plants. Thus, I bind the underworld of soil to the bright world of blossoms — pollinator above, parasite below.

Often, I exploit existing tunnels; sometimes I deepen the chamber, hollowing a cell around the victim before leaving. When my larva has consumed its host in about one to two weeks, it spins a cocoon underground and overwinters within. In spring it pupates, the metamorphosis complete in hidden darkness. 

I measure perhaps 15 to 25 mm in length, depending on region, and I am most commonly seen in late summer — July through September, occasionally stretching into October in warmer regions. I occur across eastern and central North America — from New England to the Plains, south into the Gulf states.

In shape I carry a slight bend — a posture echoed in my family name. Scolia shares a root with “scoliosis,” and our bent stance is a field guide clue to memory. My wings show subtle corrugations: parallel ridges along the outer halves, another fingerprint of the Scoliidae.

My gender reveals outward secrets. Males have longer antennae (13 segments) versus females’ 12, and a retractable pseudo-stinger — three prongs that mimic the tool but cannot deliver the venom: females alone carry the true sting. Males often emerge earlier, patrolling low flights in lazy figure-eight loops or hovering near scent trails. Some may roost singly or in loose clusters upon stems or twigs at dusk.

I exist at a liminal crossing: above ground I drift among flowers, below ground I tend life and death in hidden soil. I come unbidden to your pollinator garden yet carry the seasons within me — blossom, grub, cocoon, flight. When your late summer blooms call, I take wing. When winter whispers, I sleep deep.

Watch for me — the wasp that is more than a wasp, the visitor of autumn you almost missed. I am Scolia bicincta, your hidden sentinel of balance, a song in flower and a secret in earth.