drone fly

from The Collaborative International Dictionary of English v.0.48

Drone fly \Drone" fly`\ (Zool.)
   A dipterous insect ({Eristalis tenax}), resembling the drone
   bee. See {Eristalis}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Eristalis \E*ris"ta*lis\, n. [NL.] (Zo["o]l.)
   A genus of dipterous insects whose young (called rat-tailed
   larv[ae]) are remarkable for their long tapering tail, which
   spiracles at the tip, and for their ability to live in very
   impure and salt waters; -- also called {drone fly}. Eristic