The mating behavior of this species was reported by Alcock (1973). The male captures large insect prey (such as a crane fly) and perches in a sunny clearing or other open area, then performs a circling flight, often with other males. Arriving females join the circling flight, eventually hovering over a single male. After contact, the prey is transferred to the female, and the male grasps the female with the middle legs about the base of the abdomen. The male grasps a twig with his front legs, supporting the pair as they hang from the perch. During mating, the modified hind legs of the male rub the tip of the female abdomen rhythmically.
Widespread in Western North America, apparently from Alaska to New Mexico, and from sea level to 4,000 m.
This species, belonging to the subgenus Enoplempis, is abundant throughout the Pacific northwest and Rocky Mountain region.
The darker, high elevation form of this species was described as Empis serperastorum by Melander (1902); this has been considered a subspecies of E. poplitea.