Why does the flower of Lonicera japonica open at dusk?

We investigated contributions of diurnal pollinators and a nocturnal pollin ator to pollen transfer in Lonicera japonica (Caprifoliaceae), whose flower s have traits typical of the hawkmoth-pollination syndrome. Diurnal bees, T etralonia nipponensis and Lasioglossum sp., delivered more pollen grains th an the nocturnal hawkmoth Theretra japonica per visit, suggesting that thes e bees were also effective pollinators. However, these bees removed over 10 times more pollen at one visit than the hawkmoth. Because of the higher po llen consumption by these bees, anthesis at dusk is considered to be optima l for Lonicera japonica to maximize overall pollen transfer under the visit ation of both nocturnal and diurnal pollinators. Tetralonin japonica disper sed color dye farther than the other pollinators, which suggests that the n octurnal pollinator contributes more to cross-pollination than the diurnal pollinators.