Abstract
This paper describes field-based observations of male-male agonistic behavior in a longlegged sac spider Cheiracanthium eutittha (Araneae: Cheiracanthidae). Males of the species exhibited a characteristic agonistic behavior, where two males hung from leaves with a dragline, with all of their long legs entangled with each other and pushed each other’s body aggressively. To the best of my knowledge, this is the first video-based report of male-male agonistic behavior associated with usage of elongated legs in this spider family.