 Therefore, it is in the female's best interest to mate with multiple males to increase the offspring genetic fitness; however, males would prefer to sire more of the females' offspring and will try to prevent the female from having multiple matings by mate guarding to exclude rival males.Similarly, the polyandrous species of spider "Pisaura mirabilis" has been demonstrated to have cryptic female choice.The presence of a nuptial gift by a male increases the proportion of sperm retained by the female (With copulation duration controlled for).