before the transient male left, whereupon the territorial male would resume its normal patrolling of his area. Male bees could switch from territoriality to transiency. Territory occupancy was not statistically observed to be dependent on tree diameter, but when territories of bees were observed and noted, trees with a diameter between 40–70 cm were observed to be used more than 20% of the time. The closely related male Eulaema bombiformis prefers trees with a mean diameter of 15.5 cm. Stern suggests this may serve as a reproductive isolating mechanism between the two species. Analysis of occupancy of territories with respect to diffuse and direct light at the site showed that territory occupancy increased with increasing diffuse light and decreasing direct light. Leks In a study conducted by Kimsey, an entomologist that specializes in bees and wasps at the University of California, Davis, she defined leks as fulfilling four criteria: 1) males aggregate and display at sites for mating; 2) males defend territories from conspecific (of the same species) males; 3) the territories do not have food or oviposition sites; and 4) the females can choose their mate. Kimsey and her team investigated E. meriana in the Canal Zone for two years. Males of this species are territorial and operate a lek system. Each selects a perch on the trunk of a tree at the edge of a temporary clearing in the forest caused by a fallen tree. None of the territories contained any flowering plants, nest sites, or nest building materials. Territories are found in treefalls or large light gaps in the tropical forest. Trees used by E. meriana were about 20–30 cm in diameter and the perch site 2-5m above the ground. The trees were noted to be relatively straight with smoothed bark. The male stands in a characteristic pose with its head close to the bark, its front and hind legs extended and its middle legs folded underneath its body. Periodically it "buzzes", vibrating its wings while opening and closing them to display the yellow abdominal markings. At intervals it takes off and flies a few meters away from the perch before looping back to land close to its previous spot. The same perches are used by males every day, both in the morning and in the afternoon, but are unoccupied for a period in the middle of the day. In ensuing years, the same spots are used