The study was conducted at 2 geothermically heated sites in British Columbia, Canada. Because of different thermal regimes, the sp. has a l-yr life cycle at Halcyon Hotsprings, and a 3-yr life cycle at Albert Canyon, At Albert Canyon, males mating early in the day did not differ significantly in size from males selected at random from the population later in the day. At Halcyon Hotsprings, males mating early in the day were significantly smaller that those selected at random later in the day. Males were also smaller, in general, at Halcyon Hotsprings than at Albert Canyon, but females were not. Differences in larval phenology may have led to changes in the relationship between male size and pairing success between the two sites. Comparative studies of lifetime mating success between populations having differing life cycles may aid in separating the effects of size, age and survivorship on mating success in nonlerritorial odonates.