Pollination of entomophilos plants of grasslands in Xilinhot,Inner Mongolia (Report of the field study under the Monbusho International Scientific Research Program)

Flower visiting insects were observed in four plant species;Leonurus sibiricus, Scutellaria scordiifolia, S. baicalensis (Lamiacear) and Hedysarum fruticosum var. lignosum (Fabaceae). Through the four species, main pollinators were workers of three species of Bombus (Hymenoptera, Apidac). A long-tongued species of Bombus was the most important pollinator for the two species, Scutellaria scordiifolia and S. baicalensis. On the other hand, other two species of short-tongued Bombus tended to visit the flowers of Leonurus sibiricus and hedysarum fruticosum var. lignosum though their pollination mechanisms were different from each other (nototribic vs. sternotribic). These showed that their selective pollination is closely related to correlation between tongue lengths of bees and flower tube lengths of the plants. In the population where Leonurus sibiricus and Scutellaria scordiifolia grew together, the bees foraged more discriminately than where each was alone. In this case, resource partitioning of the bees was clearer. In the two species of Scutellaria, nectar stealing behavior by the long-tongued species of Bombus was also observed