 Lice were ubiquitous in human society until at least the Middle Ages . They appear in folktales , songs such as The Kilkenny Louse House , and novels such as James Joyce 's Finnegans Wake . They commonly feature in the psychiatric disorder delusional parasitosis . A louse was one of the early subjects of microscopy , appearing in Robert Hooke 's 1667 book , Micrographia . 
