noun. Any of various green aphids that are pests of cultivated plants.

noun. A bright-green fly, Musca chloris. E. D.—2. An aphid or plant-louse of various species: so called from the color.

noun. A green aphid that is a common pest of garden plants, houseplants, and crops.

noun. greenish aphid; pest on garden and crop plants

"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."

aphid  

green peach aphid  pale chrysanthemum aphid