This ultimately increases the fitness of the donor but at a great risk to the recipient. This dart changes the sperm storage ability of the receiver, not to mention the risk of injury from the dart itself. If shot in the incorrect place, the dart could puncture vital organs of the receiver resulting in permanent reproductive ability damage or death. Exogenous gifts are food items that the donor would capture or collect in order to present to the recipient. These can include seeds, prey items and leaves but can also include non-nutritive things as well like rocks. Gifts such as these increase the chances of the donors mating success and the duration of copulation. Nuptial gifts can also be classified into oral and seminal gifts. Seminal gifts may be tokens that do not have any direct value as food but may serve as an indicator of male fitness. In some species of insects such as katydids, and ground wētā the nuptial gift is packaged with the sperm of the male. The package is an edible spermatophore. These extra nutrients in the sperm are assimilated by the female and are thought to enhance the fitness of the offspring produced, thus increasing the probability that a male passes on its genes. Nuptial gifts are common in insects and other invertebrates, such as butterflies, fruit flies and katydids. They are less common in spiders, though the spider species "Pisaura mirabilis" is known for nuptial gift giving. However, this may in part be due to an experimental bias due to the ease of rearing it for experiments. Other taxa may commonly exhibit gift-giving behavior. Thus, more research is required to evaluate the scope of nuptial gifts in arachnid taxa. In many species of insects, birds and mammals, males acquire and donate food to females either before, during, or after copulation (termed mate provisioning, courtship feeding, nuptial gift giving, or meat-for-sex). Males may relinquish body parts, produce glandular secretions, or share prey or other food to gain fitness benefits via natural and sexual selection. Courtship feeding is particularly common among many bird species. Species in which the male presents the nuptial gift to the female are more common documented in the literature, however, the reverse does occur. Female Zeus bugs, "Phoreticovelia disparata," present the male with a food item before copulation. After the food item is presented to the male, he will ride on the back of the female in a small hallow.