Complex sentence: In addition to the spermatophore, males also deliver a pheromone to the female that is an antiaphrodisiac to other males, thus increasing the likelihood of the male's reproductive success.
Split into simpler sentences: In addition to the spermatophore, males also deliver a pheromone to the female that serves as an antiaphrodisiac. This compound produces an odor that deters other potential mates, thus increasing the likelihood of the male's reproductive success.