The Sierolomorphidae are a family of about 10 known species of wasps, all in the genus Sierolomorpha, found in the Northern Hemisphere. They are rare and very little is known of their biology. The coxa (basal segment of the leg) of the hind and midlegs are next to each other, and the hindwing does not have claval or jugal lobes. The first metasomal segment does not have a true node, but can appear like that of the ants. The metasomal sternum of the first segment is separated from the second by a constriction. Sexual dimorphism varies among species from slight to marked, with both males and females having wings, but females are sometimes wingless. Adults are predominantly dark brown or black in colour. They are solitary and the larvae are suspected to be ectoparasitoids of other insects.