There is a lot of weird stuff that goes on in nature. It makes no sense that God would create animals to behave in ways like this:
The male wasp spider leaves the female a tip after mating. And I don't mean like in money. Four out of five times, the male will plug up the female's genitalia with a piece of his genitalia.
Why does he do it? To try to make sure that they will be the fathers. It isn't like they can go on the Springer Show to prove the paternity of the baby spiders, because most of the time, they wind up being killed by the female regardless.
Evolution works innately on two levels. One is the survival of the species. It is why there are species today. For example, why mother crocodiles transport their young from land to water and back in their mouths without chowing down on the youngsters. The other level is the innate need for most animals to be ones directly responsible for the next generation, especially among non social male animals.
Back to the spiders, there has been a bit of an evolutionary race going on between the spiders genitals becoming able to deal with many suitors so the best sperm wins out versus the male spiders genitals evolving to make sure the mommy isn't such a slut.
Of course, the other explanation is that God is one sick mofo with too much time on his hands.
