RESOURCE PARTITIONING IN THE PARASITOID ASSEMBLAGE OF THE OAK GALLER NEUROTERUS-QUERCUSBACCARUM L (HYMENOPTERA, CYNIPIDAE)

We investigate the roles of several factors in determining patterns of parasitism on the oak galler species Neuroterus quercusbaccarum (L.). We employ exclosures around growing galls to identify the windows of vulnerability of the galler host to two primary parasitoids and one in quiline parasite. There are phenological and temporal patterns in the incidence of parasitism among the three parasite species, with the inq uiline Synergus sp. tending to attack small galls early, followed by M esopolobus tibialis which attacks medium-sized galls, and by Torymus a uratus, which attacks the largest galls. Despite the importance of gal l size in structuring the parasitoid complex, gall size does not act a s an absolute refuge from parasitism. Finally, both M. tibialis and T. auratus have significant effects on gall growth in reducing the final gall size. This result is in agreement with the idiobiontic life styl e of these species, since gall growth stops with the death of the gall maker.