These are Norfolk fairies (also called ‘highly sprites’ or ‘hikey sprites’), first recorded in print in 1872 and still remembered in a few areas of the county in the 1980s. The earliest source calls them ‘rather beneficient than otherwise’, but in most accounts they are used to scare children: ‘If you go out in the dark on your own, the hytersprites will get you’, ‘If you bain't quiet, I'll hull you to the hytersprites’, etc. They were supposed to be active in the woods at dusk. One informant said that as children she and her friends had imagined them as man-sized black bats ‘hovering silently in the twilight, waiting to snatch away disobedient children’; another had heard birdlike twitterings in the dusk, which she thought fun; a third said, ‘They are the malign spirits who enter a house if the Christmas decorations are left up after Twelfth Night, to cause destructive mischief and general ill-luck about the house for the rest of the year’.
Daniel Rabuzzi, Folklore 95 (1984), 74–89.