Black-and-yellow Mud-dauber Wasp (Sceliphron caementarium) — identification, habitat & look-alikes

The black-and-yellow mud dauber is the wasp behind the lemon- to fist-sized mud lumps on porches, eaves, barns, and bridges. It is native to North America and found throughout the US, and it is gentle: it does not defend its nest and stings only when roughly handled. Many people call it the yellow-legged mud dauber.

Appearance

Appearance: About 0.8–1.1 inches (20–28 mm) long. A black wasp with yellow marks on the thorax, the base of the antennae, and the legs, joined to the abdomen by a long, thread-thin waist. The waist is usually black, but in the desert Southwest it is often yellow. The wings are tinted brown.

Look-alikes

blue mud dauberChalybion californicum

Shiny metallic blue all over, with no yellow. It often reworks old black-and-yellow mud dauber nests rather than building its own.

Why they get mixed upBoth are thread-waisted wasps around the same mud nests.

organ pipe mud dauberTrypoxylon politum

Black with bluish wings and white "socks" on the hind legs. Its nest is a row of long, parallel mud tubes like organ pipes, not a rounded lump.

Why they get mixed upIts mud nests are just as common on walls.

Clayman's mud dauberSceliphron assimile

Its hind legs are mostly black, while the black-and-yellow mud dauber has yellow on the hind legs.

Why they get mixed upA very similar relative found from Texas south into Mexico.

Asian mud dauberSceliphron curvatum

Reddish brown with a striped abdomen, and it builds separate single mud cells instead of a clustered lump.

Why they get mixed upA newcomer from Asia, first reported in North America in the 2010s, with the same thin waist and mud nests.

Where it lives

Typical habitats: Porches and eaves
Barns and garages
Under bridges
Mud at puddle edges
Range: Found throughout the US and southern Canada, south through Mexico and Central America to the West Indies. It has been carried to Peru, parts of Europe, Japan, Australia, Hawaii, and other Pacific islands.

Behavior

Diet: Adults sip nectar, often from Queen Anne's lace and parsnips in midsummer. Larvae eat the paralyzed spiders packed into their cells.
Activity: Active in summer, usually with two or more generations a year.
Overwintering: Spends the winter as a resting larva inside the mud nest and finishes developing when the weather warms.

Life cycle

Nest: The female rolls balls of mud at puddle edges and builds tube-shaped cells side by side, up to about 25, then plasters over them to make a smooth lump.
Larva: Each cell gets one egg and several paralyzed spiders, then a thick mud plug. The larva eats the spiders in one to three weeks and spins a thin, reddish-brown cocoon.
Lifespan: Adults live about three to six weeks.