Hastings' Dictionary of the Bible (1898)
LICE. Ex 8:16. These parasitic insects are still a pest in the Nile valley. Herodotus tells us that the ancient Egyptians peculiarly abhorred such vermin, and were taught by their priests that contact with lice rendered them ceremonially unclean. Some authorities have held that gnats were here intended, but there is less ground for this opinion than for that of Sir S. W. Baker (Nile Tributaries, p.
122), which the writer's own observation inclines him to favor: "The louse that infects the human body and hair has no connection whatever with 'dust,' and if subject to a few hours' exposure to the dry heat of the burning sand it would shrivel and die; but the tick is an inhabitant of the dust — a dry, horny insect without any apparent moisture in its composition. It lives in hot sand and dust, where it cannot possibly obtain nourishment until some wretched animal should lie down upon the spot and become covered with these horrible vermin. " These ticks are much larger than lice.
The body is ordinarily about the size of a small pea; the legs are long, and the creature runs rapidly.