Wikipedia
Tidarren
Tidarren is a genus of spiders. The males are much smaller than females.
The males of this genus amputate one of their palps before maturation and enter their adult life with one palp only. It is assumed that this is done to increase mobility, as the palps are disproportionately large compared to the size of the body.
In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. Spider males use their palp to transfer semen into the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime the female feeds on the palpless male.