n. A green aphid that is a common pest of garden plants, houseplants, and crops.
The Century Dictionary and Cyclopedia
n. A bright-green fly, Musca chloris. E. D.—2. An aphid or plant-louse of various species: so called from the color.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. greenish aphid; pest on garden and crop plants
Word Usage
"The story makes it seem more like the greenfly was a human creation, but here it's suggested as something much older made possible by getting rid of the Inhibitors but possibly that's a false theory."