All males have some form of modified caudal gland used to release pheromones as part of courtship. The structure of this gland depends on the specific tribe; the organ may consist of modified caudal fin rays; modified caudal fin scales, a derived hypural fan, or modified caudal fin musculature, or combinations of the above. Modified scales may act as bellows in releasing chemicals into the water. A caudal fin ray pheromone pump, unique to tribe Glandulocaudini, consists of glandular tissue associated with modified scales and fin rays. The tribe Diapomini is the only tribe in which the caudal gland is equally developed in both the males and females.