any of a group of large, common, solitary (nonsocial) wasps in the family Sphecidae (order Hymenoptera) that are named for the stalklike anterior (front) end of the abdomen. Thread-waisted wasps are typically more than 2.5 cm (about 1 inch) long and are parasitic on insects and spiders. The host is often numbed by malaxation, a pinching or crushing of the neck by the wasp's pincerlike jaws, and paralyzed by the wasp's sting. The wasp places the host's body in a mud cell and lays an egg on it. Upon hatching, the larva consumes the host.

Members of the tribe Sphecini are often black with orange or yellow markings on the abdomen. They nest in burrows and provision their cells with caterpillars, which are eaten by the wasp larva. The mud daubers (tribe Sceliphronini) are commonly black with yellow spots and yellow legs, although some are metallic blue. They usually build several mud cells placed together in the corners of eaves or ceilings. The cells are provisioned with paralyzed spiders. Wasps of the tribe Podiini provision their cells with cockroaches, and members of the tribe Chlorionini nest in the ground and provide grasshoppers and crickets for their larvae.