Fecundity of the yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer) was studied in the greenhouse and the field using a bag cage tied over branches of white spruce trees, Picea glauca (Moench) Voss. Dissections of 279, 3–5-day-old females revealed a mean potential fecundity of 83.3 mature eggs. Females caged in the field laid 91.9% of their eggs, but females in the greenhouse laid only 61.7%. Longevity of females was 4–7 days, with 1 ♀ living 18 days. Parthenogenetic eggs developed into males. Peak oviposition in the field occurred when 80% of the new shoots were just barely retaining the bud cap. Female cocoons are significantly wider and longer than ♂ cocoons.