Theridion is a genus of tangle-web spiders with almost 600 described species around the world. Notable species are the Hawaiian happy face spider (T. grallator), named for the iconic symbol on its abdomen, and T. nigroannulatum, one of few spider species that lives in social groups, attacking prey en masse to overwhelm them as a team. Spiders in this genus are about as long or longer then they are wide. Their chelicerae have two or less teeth on the front edge and none on the back edge. The front leg is the longest in both genders, but the next longest is the second leg in males and the fourth leg in females. The epigyne can vary, but the pedipalp has a median apophysis and a colulus is absent from both genders. Philodromus cespitum, a species of running crab spider, preys on Theridion spiders in European fruit orchards.