Emergence phenology and ecology of aquatic and semi‐terrestrial insects on a boreal raised bog in Central Finland

Emergence of peatland insects was studied in Central Finland by sampling insects on a raised bog with tent traps from five different surfaces: muddy hollow without vegetation; hollow covered with Sphagnum; deep (0.7-0.9 m) open-water pool; shallow (about 0.3 m) pool with bottom covered by Carex vegetation; shallow (about 0.3 m) pool with bare muddy bottom. The material was collected at two-days intervals from 13 May until 31 August in 1981. Biomass emerging from the sites varied considerably. In general, aquatic sites were clearly more productive than semi-terrestrial sites. Corrected total biomass values for deep pools, shallow Carex pools, and shallow mud pools were 2.471, 1.066, and 0.514 g m, respectively. The corresponding values for muddy and Sphagnum hollows were 0.208 and 0.236 g m-2, respectively. All chironomids, chaoborids and trichopterans from the aquatic sites were identified to species, and their emergence phenology and habitat preferences are discussed. 14 species were considered as eurytopic littoral species, 9 species showed strong preference for the bog pools or polyhumic lakes, and 8 species were of diverse origin. Differences in emergence patterns and habitat preferences are probably connected with species-specific resistances to freezing and oxygen and nutrient requirements. The role of emerging insects in the peatland food webs, especially as food for breeding birds, is briefly discussed.