Hair-pencils are specialized structures involved in pheromone signaling, commonly found in male moths and butterflies. These structures release pheromones that function dually as aphrodisiacs and tranquilizers for females, while concurrently acting as repellents to conspecific males. The glands responsible for producing these pheromones are housed within the male's body until the initiation of courtship, at which juncture they are expelled through sclerotized levers located on the abdomen.

Not to be confused with coremata, which are distinct structures unique to male moths that bears hair-pencils.