Studies on the insects visiting apple flower at Nasu, Tochigi Prefecture

Abstract

The insects visiting apple flower were investigated at Kuroiso Branch of the Tochigi Agricultural Experiment Station during May 11 -May 17 in 1965. The results obtained are summarized as follows:1) The weather conditions during the period of observation were favorable for the flying activities of insect visitors, without remarkable deviation of air temperature and prevalence of fine and calm days.2) For the reason of abnormal low temperature in the early spring, the blooming period of all varieties used in this study delayed about 10 days than in an average year, though the amount of blossoms was relatively abundant.3) The insect visitors collected in this work were mostly hymenopterous and dipterous insects. Total individual number of Hymenoptera is 2018, that is, 8.3 times as large as that of Diptera. Iyymenopterous visitors belong to 45 species (5 families, 12 genera), while dipterous visitors belong to 17 species (5 families, 14 genera).4) The important visitors in Hymenoptera are arranged in the descending order as follows:Andrena opacifovea, Apis mellifera (honey bee), A. kaguya, Lasioglossum trispine, L. subfamiliare-complex, L. sp. ad. discrepans, A. sasakii, A. hebes, A. dentata, and Xylocopa appendiculata cirumvolans (cf. Table 3).The most numerous visitor of Diptera is Tubiferacerealis, then Bibio rufiventris is next, and other species are very scarce in number (cf. Table 4).5) Four species of Andrenid bees, A. opacifovea, A. sasakii, A. dentata and A. hebes are the mediumsized bees, as large as or slightly smaller than honey bee. Their total numbers reach 872 and occupying 43.2% of Hymenoptera. Further their visiting activities are very rapid and vigorous (=very quick and restless movements on flowers). Therefore they seem to be the most efficient visitors.6) Halictid bees seem to be inferior to Andrenid bees in pollinating efficiency because of smaller sizes, though they are numerous and their visiting activities are rapid and vigorous.\7) Both Tubifera cerealis and Bibio rufiventris are the dominant visitors in Diptera, but Bibio rufiventris is supposedly not an important pollinator, judging from their very sluggish activities. On the other hand, Tubifera cerealis is relatively active, so that it seems to be the most important pollinator among Diptera.