The orb-web spider Nephilengys malabarensis is sexually cannibalistic and the male has detachable genitals.
These spiders have at most two chances to mate: They have a pair of sperm-transferring organs, actually called their "palps" but analogous to a penis, which detach from their bodies when they disengage from mating — either when the female pushes them away and possibly eats them or they successfully run away to risk death another day."
http://www.huffingto...f=weird-animals
