The Collaborative International Dictionary
Eristalis tenax
Drone fly \Drone" fly`\ (Zo["o]l.) A dipterous insect ( Eristalis tenax), resembling the drone bee. See Eristalis.
Wikipedia
Eristalis tenax
Eristalis tenax is a European hoverfly, also known as the drone fly (or "dronefly"). It has been introduced into North America and is widely established.