The head and mesosoma are reddish-brown or orange-brown while the posterior parts of the wasp are black, the limbs and antennae are blackish brown.

The forelegs are largely orange brown but the rest of the legs are uniformly black.

[3] The wasp was originally collected by the expedition of Captain James Cook in 1768 and the specimens were described by Johan Christian Fabricius in 1775, and then largely forgotten.

A wasp was then observed dragging a redback spider to its nest in a garden in Beaconsfield Western Australia in 2010.

[3] Agenioideus nigricornis is found in Australia where it is widespread but it is apparently absent from Tasmania.