Abstract
The effects of fluctuating water tables on the survival of the larch sawfly, Pristiphora erichsonii (Hartig) (Hymenoptera: Tenthredinidae), were studied by burying cocoons at different depths in a tamarack bog. Most larvae in cocoons flooded during August or September died before winter. The percentage of overwintering survival of unflooded cocoons remained constant from late fall until development began in the spring. The higher the cocoons were above the maximum water table during August and September, the greater was the percentage of overwintering survival and subsequent adult emergence.