Nasonia are a genus of small pteromalid parasitoid wasps that sting and lay eggs in the pupae of various flies. The fly species that Nasonia usually parasitize are primarily blow flies and flesh flies, making Nasonia a useful tool for biocontrol of these pest flies. The small match-head sized wasps are also referred to as jewel wasps based on the emerald sheen of their exoskeleton (visible in the image to the right).