We compared flower visitation patterns of two coexisting honey bees, Apis mellifera Linnaeus and Apis cerana japonica Radoszkowski, on 20 plant species, including three exotics, under natural conditions in Nara, Japan, from April to August 2012. We also measured flower color based on bee color vision (15 flower species), nectar volume (nine species) and nectar concentration (eight species). Flowers colored white, pink, red, purple and cream were classified as bee‐blue‐green, and yellow was classified as bee‐green. Apis cerana visited 14 plant species and A. mellifera visited 11. Although the two Apis species are similar in morphology, they visited different plants: in particular, A. cerana visited native plant species more often than did A. mellifera. Both A. mellifera and A. cerana visited not only nectariferous flowers but also those with no nectar. We also found different visitation patterns between A. cerana and A. mellifera: Apis cerana more often visited flowers with smaller color angle (bee‐blue‐green), lower chroma and higher brightness, and flowers secreting nectars of higher concentration and smaller volume than did A. mellifera.

While the majority of angiosperm plants have hermaphrodite flowers where a single pollinator visit can achieve both pollen removal and deposition, 5–6% of angiosperms including zoophilous species are dioecious, necessitating pollen transport from male plants to females. As such, dioecy is considered less adaptive under low temperature conditions that tend to restrict or lower potential pollinator activity. Interestingly, however, a number of dioecious, zoophilous plants including <i>Eurya japonica</i> Thunb. (Pentaphylacaceae) bloom in low temperature seasons. This study made a quantitative assessment of flower visitors/pollinators of <i>E. japonica</i> blooming in early spring in central Japan. A total of 15 families in 4 orders of insects were recorded on both pistillate and staminate flowers of <i>E. japonica</i>, of which Diptera (Empididae and Chironomidae, in particular) and Hymenoptera were predominant regardless of site/year. Hymenopteran visitors were more active at higher temperatures, while dipterans were observed even at low temperatures. The fruiting rate and the number of seeds were greater at the site where dipteran visitors were more abundant. The present study suggests that the system of multi-taxa, Diptera-dominated pollination may play an important role in the reproductive ecology of dioecious plant species, in particular those flowering at low temperatures.