BIOLOGY OF THE ROSE STEM GALLER DIPLOLEPIS-NODULOSA (HYMENOPTERA, CYNIPIDAE) AND ITS ASSOCIATED COMPONENT COMMUNITY IN CENTRAL ONTARIO

Diplolepis nodulosa (Beutenmuller) induces small, monothalamous, proso plasmic galls in stem tissues of Rosa blanda Aiton. Adults and galls a re redescribed and notes on distribution, host records, morphological variation, and a comparison with related species are presented. Galls are commonly attacked by the inquiline Periclistus pirata (Osten Sacke n). Data on life history and mortality of inducers and inquilines, alo ng with seasonal variation in gall density, were obtained from a study site near Sudbury, Ontario, in 1993 and 1994. Inquilines killed 55% o f the inducer population in 1993 and 65% in 1994. The abundance and de nsity of galls fluctuated over the 2 years; however, the proportion of galls modified by inquilines remained constant. Six species of parasi toids caused an additional 17% inducer mortality. Aprostocetus sp. was the dominant parasitoid of D. nodulosa, whereas the other five specie s were incidental. The assemblage of parasitoids associated with galls modified by P. pirata caused 13% inquiline mortality and include seve n species, of which Eurytoma spp. and Caenacis sp. were dominant. The unique aspects of the D. nodulosa gall system are discussed.