What is "chrysogaster"

Chrysogaster is a genus of small hoverflies in the subfamily Eristalinae. They are dark or black with shiny colourful reflections and can often be seen visiting flowers in damp marshy areas where the aquatic larvae live. Species in the related genera Melanogaster, Orthonevra, Lejogaster and Riponnensia were formerly treated as members of Chrysogaster.