Syrphid flies are also known as flower or hover flies because they visit flowers to feed on nectar and pollen. The most common species in Pacific Northwest orchards is Scaeva pyrastri. Adults are not predaceous, but the larvae prey on aphids, scale insects and thrips. Syrphid fly larvae may quickly suppress aphid infestations, as each is capable of destroying hundreds of aphids during its development. Where lady beetles are not abundant, syrphid fly larvae usually become the dominant predator.
The western European hoverfly fauna is very well understood, as this free upload from the Syrpth the net database shows. May be of some family level use for you.