In this paper, the results of comparative studies on the flower-visiting habits of Japanese bees are described with special reference to some problems, namely : flower-visiting period, visiting object, preference to flower-species, and also, status as flower-visiting bee or value as pollinator. (1) Flower-visiting activities of Japanese bees start by Apis indica japonica in February and finish with Bombus diversus in November. Some species of Apidae, Halictidae, and Megachilidae have considerably long flower-visiting periods (Table 1). (2) Numerous species of Japanese bees visited flowers during the periods of May (39 species) and June (36 species) (Table 2). Moreover, the number of individuals of flower-visiting bees showed the maximum population in the periods of April-July and September-October, respectively. (3) The maximum number of flower-species visited in a month was shown by the workers of B. diversus. That is, the workers of B. diversus visited the flowers of 30 species respectively in June and July, and they were followed by Xylocopa appendiculata circumvolans (20 and 22 species respectively in May and June), Tetralonia nipponensis (20 species in June), and Halictus scitulus (22 and 24 species respectively in May and June) (Table 4). (4) Total number of flower-species visited by 52 bee-species in each month, were recorded as follows : 320 flower-species in May, 241 species in June, 172 species in April, 111 species in September, and 101 species in July (Table 4). (5) Most flowers with rather long flowering period were included in Compositae (8 months), Labiatae (7 months), Leguminosae (7 months), and Rosaceae (6 months). And, most Japanese bees visited predominantly the flowers of Leguminosae (125 species in total), Compositae (118 species), Rosaceae (97 species), and Labiatae (52 species) (Table 3). (6) On the preference of Apoidea to flowers, it may be summarized as follows. The preferences were shown to the flowers of Compositae, Cruciferae, Rosaceae, and Ranunculaceae by the bees of Colletidae, Andrenidae, Halictidae, and two genera of cuckoo bee, Nomada and Epeolus. On the other hand, the bees of Megachilidae and Apidae preferred the flowers of Leguminosae. Moreover, the bees of Apidae, except oligolectic species, visited also dominantly various flowers of Compositae, Rosaceae, Labiatae, Caprifoliaceae, and so on (Tables 5 and 6). (7) Apoidea includes numerous species belonging to various grades of morphological and ethological development, although they all seem to take part in pollination of both cultivated and wild plants. It is supposed that all these bees and entomophilous flowers go on well with each other in natural condition only when bees and flowers of various grades of development are present. Eventually it may be concluded that all bee species should be preserved and be kept not to be prevented in their natural multiplication, and consequently that a favorable environment with plentiful flora of flowering plants should be preserved. The more abundant species of bee pollinators and entomophilous flowers the habitat comprises, the better the relation between them may be expected. Only under such environment, therefore, the pollination may be supposed to be carried out normally by special species of bees suitable for respective species of the so-called useful plants.
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