BIOLOGY OF THE ROSE STEM GALLERDIPLOLEPIS NODULOSA(HYMENOPTERA: CYNIPIDAE) AND ITS ASSOCIATED COMPONENT COMMUNITY IN CENTRAL ONTARIO

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Abstract
Diplolepis nodulosa(Beutenmüller) induces small, monothalamous, prosoplasmic galls in stem tissues ofRosa blandaAiton. Adults and galls are redescribed and notes on distribution, host records, morphological variation, and a comparison with related species are presented. Galls are commonly attacked by the inquilinePericlistus pirata(Osten Sacken). Data on life history and mortality of inducers and inquilines, along with seasonal variation in gall density, were obtained from a study site near Sudbury. Ontario, in 1993 and 1994. Inquilines killed 55% of the inducer population in 1993 and 65% in 1994. The abundance and density of galls fluctuated over the 2 years; however, the proportion of galls modified by inquilines remained constant. Six species of parasitoids caused an additional 17% inducer mortality.Aprostocetussp. was the dominant parasitoid ofD.nodulosa, whereas the other five species were incidental. The assemblage of parasitoids associated with galls modified byP.piratacaused 13% inquiline mortality and include seven species, of whichEurytomaspp. andCaenacissp. were dominant. The unique aspects of theD.nodulosagall system are discussed.