We compared insect visitors to 10 different flower species filmed simultaneously at two sites to assess whether insect taxa visiting at the two locations differed on a fine scale (<400 m apart). Although each of the 10 flower species had some insect taxa that were shared between sites, each also had unique visitors that appeared at a single site. Both the flowers and their insect visitors were generalists. Flowers were visited by an average of 16 different insect taxa. Insect taxa were observed visiting an average of three to four different flower species. The heterogeneity of floral visitors between sites is consistent with our proposed neighborhood model of pollination where flowers draw on insects in their area for pollination services and insects forage for nectar and pollen from flower species in their home ranges. Temporal heterogeneity can be dramatic. We recorded an influx of painted lady butterflies, which arrived in abundance on 12 June and were absent prior to then. Painted ladies dominated visits to flowers with hidden nectar sources (e.g., pale corydalis, blueberry, and bearberry). Spatial and temporal differences in insect visitors suggest ecological flexibility in pollination systems and may be important in insuring the persistence of flowers and insect visitors. Heterogeneity of insect visitors on a fine scale may structure gene flow among flowers and set the stage for local speciation in the angiosperms. The variation in the visitor community between sites highlights the importance of preserving multiple sites to insure the conservation of flowers and their insect visitors.