On 7th of July 2011, I noticed these two female parasitoid wasps (Protichneumon grandis) while walking along the Orange Trail of the State Botanical Garden of Georgia. They were fighting with each other to lay their eggs inside a crack of a log using their long ovipositors. One had a pretty good grip. The other was very grumpy for not having access to the crack. These wasps are said to parasitize a sphingid moth species the Rosy Maple Moth (Dryocampa rubicunda).
This observation is a good basis for discussing when members of the same species cooperate and defect and even become antagonistic. Competition is toughest among members of the same species (intraspesific competition) because they have identical needs (in this case a rare crack containing the prey). In this observation the situation is fairly simple to interpret. However, evolutionary roots of female aggression in humans is an understudied curious topic.