Virginia Bluebells, Mertensia virginica, (L) Pers. is a herbaceous perennial that grows along streams and moist hillsides within the deciduous forests of the Northeastern United States. M. virginica produces a maximum of four nutlets per flower and is visited by a variety of insect species, some of which exhibit nectar robbing behavior. Nectar robbing is a behavior by which insects obtain nectar from flowers without contacting the reproductive parts of the flowers and has been extensively reported in the literature. In 1997, 13 patches (four contained one plant, three contained five plants, three contained ten plants, and three contained 20 plants) were chosen within the Horner Wildlife Sanctuary in Oldham County, Kentucky USA where M. virginica blooms for approximately four weeks during the month of April. The flowers in each patch were monitored and visitation rates of nectar robbing insects and non-nectar robbing insects were calculated. The effects on seed set of nectar robbed vs. non-nectar robbed flowers in the different patch sizes were compared as well. Comparisons were carried out using ANOVA statiscal procedures in SAS. Twelve insect species were found to visit M. virginica, although Bombus bimaculatus (non-nectar robber) and B. affinis (nectar robber) together accounted for over 70% of all visits regardless of patch size. B. bimaculatus spent an average of 6.09 seconds per flower. B. affinis spent an average of 9.7 seconds per flower on their initial visit and 4.8 seconds on their visit to a previously robbed flower. In contrast to most studies of other flower species in the literature, nectar robbery in M. virginica was found to significantly increase seed set across all patch sizes.

Key words: bluebells, Bombus, Boragenaceae, Mertensia virginica, nectar robbery, patch size