Even the spiders understood it.! to

The males of some insects and spiders present “marriage gifts” to the females during the breeding. Usually this is a fresh-fished prey that the female eats during copulation, but sometimes the males cheat their girlfriends by adding uneatable items to them. To mislead the female helps bright packaging of the web, in which the male spiders wrap their gifts. As it turned out, females are equally willing to pair with cavaliers offering real and "symbolic" gifts, while males without gifts have twice as much chance.
However, a female who receives an uneatable gift stops copulation faster, which reduces the reproductive success of male deceivers: they have time to pass on to their partner less sperm than their competitors, who spent time and effort on obtaining the real, nutritious gift.
Apparently, this is what explains the fact that most males still prefer to give good gifts to females.