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 −2 , 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.