Length: wasp in top photos 10 mm
Entomologist R. A. Cushman erected genus Messatoporus in 1929, "defined mainly by the broadly truncate clypeus, mandible very long with dorsal tooth much longer than ventral tooth, propodeum transversely striated, areolet small and first metasomal tergite long, with spiracle near the middle." The included species were North American (Santos and Aguiar, 2013).
Since the original description, many new species have been described. Today the genus contains 89 described species, distributed from Canada to southern South America. The genus is monophyletic.
The species pictured here, Messatoporus discoidalis, is a parasitoid of mud-nesting Pomilid spider wasps. Among the documented host species are Ageniella conflicta, Phanagenia bombycina, Auplopus mellipes, and Ceropales maculata (Santos and Augiar, 2013).
Photos notes: the upper two photos are of a female, and were taken on 12 October 2010. The bottom two are of a male, and were taken on 16 July 2010. Both were taken in Upshur County, West Virginia.
American Insects site