Connectivity in aquatic ecosystems is a broad concept that refers to the transfer of both abiotic (i.e. matter and energy) and biotic (organisms) elements through the landscape across a range of spatial and temporal scales. The present study focuses on the patterns of connectivity between populations of aquatic insects in headwater streams. Dispersal, emigration and immigration are the demographic forms of population connectivity, which are largely thought to be by the winged adult stages that spend much of their lives in the riparian zone. These flying adults may disperse laterally and longitudinally to circumvent terrestrial barriers between headwater streams and catchments, thus allowing gene flow between populations in different streams. Riparian vegetation has a potentially strong influence on the survival and success of adult stages through the alteration of the microclimate, habitat structure and potential food sources. Habitat fragmentation caused by forest harvesting can reduce population connectivity by increasing the area of open forest and altering microclimatic conditions, particularly air temperature and humidity. Degradation of adjacent terrestrial habitat through forest harvesting may egatively affect adult dispersal because altered microclimatic conditions may create a barrier to dispersal. For example, the extreme conditions caused by harvesting may exceed tolerance limits of adult aquatic insects. In addition, aquatic insect life history traits may influence the degree to which forest harvesting affects their populations. For example, if a species with a short emergence period emerges during peak summer temperatures, temperatures could be higher in cleared areas compared to forested, thus exceeding the tolerance limit of the species. However, little direct evidence exists on the effects of selective harvesting and the associated changes to the microclimate on adult dispersal and genetic population connectedness.