Why the eversion of the endophallus of honey bee drone stops at the partly everted stage and significance of this

Abstract - After the drones are excited, they evert the endophallus, which mostly stops at partly everted stage with a slender tip at the end. The reason of the stop and the appearance of the tip is not known. There are transversal hairy folds at the ventral border of the cervix of honeybee drone endophallus. They form a duct inside the cervix. The dorsal walls of the duct come together at an acute angle and join at the summit quite tight. During partial eversion, the cervical duct appears at the end; however, its dorsal walls do not open (separate). The diameter of the duct is 0.4–0.5 mm. The bulb of the endophallus is not able to pass through such a small duct and therefore the eversion stops. Only after the pressure inside partly everted endophallus is increased sufficiently, the dorsal walls of the duct are opened, the interior of the cervix is enlarged and the bulb passes through it, which results in full eversion. The increased pressure inside the endophallus results in the semen being ejected with greater force. This is important during multiple matings of queen bees.