14 species in North America, all in the genus Pseudomasaris.
Yellow and black. FW with only two submarginal cells. Clubbed antennae.
The larvae- unlike those of other Vespids- eat pollen and nectar instead of insects, etc.
The females make nests of mud or sand attached to twigs or rocks. They provision the nests with pollen and nectar and lay their eggs. The eggs hatch into larvae that eat the provisions, then pupate and emerge as adults.
Bradley, J. C. (1922). The taxonomy of the Masarid wasps, including a monograph of the North American species. Univ. Cal. Publ. in Entomol. Vol. 1, No. 9, pp369-464. (Full Text
Richards, O.W. (1963). The Species Pseudomasaris Ashmead (Hymenoptera, Masaridae). U.C. Press. - Contains key to species.
Richards, O.W. (1966). New records of Pseudomasaris Ashmead (Hymenoptera: Vespoidea, Masaridae), with notes on P. phaceliae Rohwer and P. cazieri R.M. Bohart. Proc. Royal Ent. Soc. London (B), 35 (3-4), pp. 47-55.
Gess, Sarah K. (1996). The Pollen Wasps - Ecology and Natural History of the Masarinae. Harvard University Press. (1)
Carpenter, J.M. (2001). Checklist of species of the subfamily Masarinae (Hymenoptera, Vespidae). American Museum novitates; no. 3325. (Full Text