What is "hair-pencil"

Hair-pencils and coremata are pheromone signaling structures present in lepidopteran males. Males use hair-pencils in courtship behaviors with females, the pheromones excreted by the hair-pencils serve as both aphrodisiacs and tranquilizers to females as well as repellents to conspecific males. Hair-pencil glands are stored inside the male until courtship begins, at which point they are forced out of the body by sclerotized levers present on the abdomen. Coremata (the singular form being corema) are very similar structures. Their exact definition is confused by early descriptions but they are more specifically defined as the internal, glandular, eversible structures that bear the hair-pencils and can be voluntarily inflated with hemolymph or air.