The most interesting researching is being done on the Australian Redback Spider.
Redback males seem to facilitate sexual cannibalism.
Redback copulation consists of the male placing his 2 palps into the female's genital openings, one at a time. The male then spins 180 degrees and places his abdomen directly over the female's mouthparts. This manuver allows the female easy-access feeding. Cannibalism results in longer copulation duration. Dampening the female's desire to mate again.