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

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Abstract
Two naturalized populations and two planted populations of Rosa rugosa Thunb. were studied with respect to chalcid seed wasp infestation. Megastigmus nigrovariegatus Ashmead was found in hips from planted R. rugosa in Halifax and Dartmouth, Nova Scotia, but not from bushes at naturalized sites. The percentage of infested hips at the Halifax and Dartmouth locations was 26 and 31%, respectively. The percentage of infested achenes within a single hip varied widely from 3 to 79% at the Halifax 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 wall 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 was observed ovipositing on a single hip.