Wikipedia
The Sapygidae are a family of solitary aculeate wasps. There does not seem to be a common English name, but club-horned wasps (translating the German name Keulhornwespen - in reference to the distinctive thickening of the antennae) seems as good a name as any, though various other groups of wasps also have clubbed or thickened antennae. They are generally black wasps, similar in appearance to some Tiphiidae, with white or yellow markings developed to various degrees.
The female oviposits her eggs into the nests of solitary bees, and the developing larvae consume both the host larvae and the supply of food provided for them.
The Sapygidae are a small family with only about 80 species described, and they are not of major economic importance. However, some of their host species are important pollinators, and it may sometimes be necessary to control the level of predation on them. (Peterson et al., 1992).
Fossil sapygids have been found in Upper Eocene Baltic amber (Brischke, 1886).