The behavioral ecology of Libellula luctuosa (Burmeister) (Odonata: Anisoptera) was studied at several ponds in northern New York State, U.S.A. The male Libellula maintained territories which were slightly overlapping on each pond. As many as six males utilized each territorial sector of the pond concurrently. Conspecifics showing submissive behavior were allowed on the mating site, and all males on the territory recognized and maintained the boundaries. These communal sites were primarily mating/ovipositing areas. Aggressive interactions among co-occurring males resulted in the establishment of a dominance hierarchy on each territory. The dominance hierarchy increased the reproductive efficiency of the dominant male probably by reducing interference with mating. Subordinate males occasionally mated. The relative advantage of dominance in mating attempts is quantified. The average number of males at the pond changed little during the day and males did not localize their behavior to specific parts of the pond. An individual male returned to the pond an average of 5 different days. While at the water, males either flew over a territory or perched adjacent to the pond. Individuals frequently left the pond and returned during the day. The amount of time spent in each activity depended on the time of day and number of conspecific competitors. Site attachment was low and males commonly flew to different territorial sectors. The dominance status of individual males often changed quite rapidly, especially when changing sectors or upon returning to the pond. Female Libellula occurred at low average daily density and showed no preference for specific areas of the pond or for certain times of day. Time budgets and analyses of mating behavior of Libellula luctuosa are considered with regard to the males' response to the availability and predictability of females and mating/ ovipositing sites. The behavioral patterns are analyzed with reference to a time-energymaturational-experiential hypothesis for the evolution of the behavior. Extensive comparisons are made between Libellula luctuosa (Burmeister) and Plathemis lydia (Drury).