Total insect emergence from subalpine Findley Lake during warm and cold years

Insects were collected in floating emergence traps on oligotrophic Findley Lake in the coniferous forest of the Cascade Mountains.  There was considerable yearly variation in the date of the thaw, the maximum surface temperature and the depth to which the warm surface water mixed during the summer.  The maximum number emerged from the warmest sites, the sites that thawed long before the rest of the lake and the sites that had the most organic detritus from the surrounding forest.  The total number that emerged in 1973 when there was an early thaw on June 7 and a maximum surface temperature of 19.25 degrees was 3.0 times as much as in 1974 when there was a late thaw on July 31 and a maximum surface temperature of only 12.5 degrees.  The maximum biomass emerged from the sites that had the most organic detritus, the sites that thawed long before the rest of the lake and the solid bottom.  The biomass that emerged in the warm year of 1973 was 3.3 times as much as in the cold year of 1974.  The peak biomass emerged from deeper water after an early thaw than after a late thaw.