Vicious, biting, parasitic insects, Morgai Flies (BS."Suskoi") were one of the nasty nuisances of life in Mordor. They could found all over the Black Land, particularly in Gorgoroth, where they were known as Orcflies. Their sole food was blood, but they enjoyed feeding off nearly any beast they could find.
Relatives of common Horseflies, Morgai Flies were large and dun, gray, or black in color, with red eyes and a red blotch, like Sauron's Lidless Eye, on their backs. Many chroniclers believed them to be monsters of the Dark Lord's design. This might have been true of some of the larger subgroups, but those of the basic variety were simply huge, primeval vermin.