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Too busy to pester - Bembix wasps

Updated: Aug 17, 2021

By Pamela Sleightholm

When we think about wasps, many of us will remember a run-in – an annoying buzz around a picnic or an inconveniently placed nest. These are the social wasps – living together with great interest in humans and our food.

But there’s another kind of wasp whose lives and work generally go unnoticed by humans – Bembix americana, or sand wasps. If you have bare sandy soil in your garden, the sand wasps may be hard at work below the surface, digging tunnels and nests for their young.

Bembix wasp on coneflower, photo by Peeter Poldre 2021.

They’re solitary predators that primarily target flies – including the dreaded horse and deer flies – for their developing larvae. Mother sand wasps are pollinators, fuelling themselves with flower nectar. The flies they hunt are delivered to their larvae, each one given its own tunnel created by its mother and sealed to keep it safe. When a larva finishes one fly, mother returns with another for it to consume – up to 20 flies over 2 weeks.

She digs, hunts and conceals the tunnels for her young. She can recognize her own tunnels based on landmarks, and may need to reorient after heavy rains have altered the landscape. When the larvae mature, the tunnel is sealed for the winter. They pupate in spring and come out from their tunnels in summer.

Bembix wasps are doting parents in the insect world – and it’s this busy life that keeps them from “interfering” in our lives as some of their wasp cousins are prone to do.



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