Functional morphology of the penis of Celithemis eponina (Drury) (Anisoptera: Libellulidae)

A description is given of the anatomy of the penis and of associated secondary genital structures. The penis of Anisoptera is not homologous with that of Zygoptera, and it consists of a 4-segmented organ with inflatable structures on the last segment. The hamuli and the anterior frame cooperate to swing the ligula ventrally and this action in turn thrusts the penis posteriorly. The same movement also causes a hamular claw to close, and this is believed to grasp a rim on the female’s genital plate during copulation. The penis cannot be withdrawn without the grasp being loosened. Rhythmical movements which appear in stage 1 of copulation are interpreted to represent activity which packs previously deposited sperm down in the female tract, and it is suggested that sperm removal is less important in this species than the displacement of sperm within the female tract.