At Alexandra Fiord, Ellesmere Island, the diving beetles Hydroporus morio Aubé and Hydroporus polaris Fall occur in a series of shallow ponds. Detailed habitat measurements of a temporary and a permanent pond revealed a more complex and extensive organic substrate and vegetation community, longer developmental time, and greater thermal budget in the permanent pond. Hydroporus polaris was most abundant in the temporary pond, but occurred in both; this species oviposited in the absence of macrophytic vegetation, completed larval development quickly, and pupated in the drying pond substrate, and adults dispersed in fall to moister overwintering sites. Hydroporus morio was restricted to the single permanent pond; this species took longer to complete larval development, pupated in wet moss, and overwintered as adults encased in ice on the vertical pond edge. We hypothesize that H. morio is excluded from temporary ponds in the arctic by its requirement for a relatively long development time. Alternatively, H. morio may require sheltered overwintering sites that temporary ponds do not offer.