Faunal makeup of wild bees and their flower utilization in a semi-urbanized area in central Japan

The species composition of wild bees and their flower utilization patterns were surveyed from April to November in 1996 in a semi‐urbanized area adjacent to Sugao Marsh, Ibaraki, central Japan. A total of 750 individuals belonging to 43 species in six families were collected. The most dominant family was Halictidae, for which 13 species and 251 individuals were collected. The most dominant species was Colletes patellatus (120 individuals) of the Colletidae. The results at Sugao were compared with those obtained from three other areas of Ibaraki Prefecture, which have similar climatic conditions, yet have different environmental characteristics in terms of human impact. The four sites in Ibaraki can be classified into two groups: the first comprising Sugao and Mito in cultivated and/or human‐dwelling areas, and the second comprising Yamizo and Gozen’yama, in forest areas with more natural elements. The number of species at Sugao was the smallest among the four study sites. On the other hand, the values for species evenness at Sugao were the second‐highest of the four study sites. These findings show that the different characteristics of different bee communities reflect their local environmental conditions, including their floral compositions. The bees visited 36 flower species in 20 families, and 70.7% of all individuals studied visited Compositae flowers. The heavy utilization of composite flowers is possibly because of the existence of a simplified flora consisting of a few dominant composite plant species. Among these plants, Solidago altissima and Lactuca indica made large contributions to supporting autumn bees, especially Colletes patellatus and Colletes perforator, which are solitary and oligolectic on Compositae.