Species Sceliphron caementarium - Yellow-legged Mud-dauber Wasp

Black-and-yellow Mud-dauber (note: this name also applies to almost every species in the genus so is a very poor name for a particular species)

Black-waisted Mud-dauber (note: often used outside of the Americas where this is a unique trait; this trait is useless in the Americas where most of our species have black petioles and where the desert southwest population of S. caementarium often has a yellow petiole)

Sceliphron caementarium (Drury 1773)

24-28 mm

Black body with variable amount of yellow markings. Pedicel (waist) about twice as long as the rest of the abdomen. In all cases, the hind legs are marked with copious yellow on the tibiae and tarsi.

Tips on how to determine sex:

Throughout NA (s. Can. to C. Amer. and W. Indies) - Map (1)(2); accidentally introduced into Europe several times, well established in several countries since the 1970s(3)

Adults nectar at flowers; mud nests are built in all kinds of sheltered locations, incl. man-made structures, rock ledges, etc. Adults collect mud for nests at puddle/pool edges.(4)(5)

mostly: Apr-Oct (2)

Nests are provisioned with spiders; adults common at flowers(4), especially parsnip and water parsnip, and visit hummingbird feeders.(5)

Nests may comprise up to 25 cylindrical cells, with typically 6-15 (up to 40) prey spiders per cell. The female may provide the cells with a temporary closure (a thin mud curtain) to keep out parasites while she is collecting prey. Once the cell is stocked, she lays an egg on one of the last prey and seals the cell with a thick mud plug. She may then add more mud to cover the entire cluster of cells.(5)

Adults are common where water splashes on bare soil (MAQ, pers. obs., 2019).

Though the species is globally known for its black petiole, a population in the western US (OR, CA, NV, UT, AZ, CO; rarely TX) has a yellow petiole instead.

In Texas, from the Rio Grande Valley north to about San Antonio, S. assimile co-occurs. S. assimile is noted for its entirely black, to nearly-so, hind legs.