THE CHALCID SEED WASP, MEGASTIGMUS-NIGROVARIEGATUS HYMENOPTERA - TORYMIDAE, ON ROSA-RUGOSA THUNB. IN NOVA-SCOTIA

Two naturalized populations and two planted populations of Rosa rugosa Thunb. were studied with respect to chalcid seed wasp infestation. Me gastigmus nigrovariegatus Ashmead was found in hips from planted R. ru gosa in Halifax and Dartmouth, Nova Scotia, but not from bushes at nat uralized sites. The percentage of infested hips at the Halifax and Dar tmouth locations was 26 and 31%, respectively. The percentage of infes ted achenes within a single hip varied widely from 3 to 79% at the Hal ifax site and 7 to 60% at the Dartmouth site. Adult emergence was over 75% successful when achenes were over 2 mm in diameter but less than 15% for smaller achenes. The exit hole on the achene faced the outer w all of the hip. Adults emerged later in Nova Scotia than in the United States and between 59 and 72% were female. More than one adult wasp w as observed ovipositing on a single hip.