シロオビツツハナバチ

1. In this paper the life-history of Osmia excavata Alfken was described. The flight of Osmia excavata Alfken begins in late March or early April and lasts as late as end April or early May. Usually they nest gregariously. Before starting her nesting activity, the female bee copulates once. No copulation has been observed whenever the female bee begins to nest. Dried bamboo stem or reed is selected for the nest, the diameter of which varies from 4.5 to 20 mm. The larval cell (Fig. 2) is composed of mud-partition and pollen-honey mass, on which an elongate egg is deposited. The mud-partition is 2-3 mm. thick. It is completed within 40 minutes in average in which about 8 mud collecting flights are included. Pollen and honey are usually collected from Brassica campestris. The bee spends about three hours to preserve pollen-honey mass for one larval cell on a fine, windless day. A single trip for collecting pollen and honey needs about 9 minutes. When food for an offspring is prepared sufficiently, the oviposition follows immediately. Respiration seems to be stopped during oviposition, which continues about 1 minute. A female bee completes one to two larval cells, namely, she deposits one to two eggs, in a day. About 25 or more eggs are laid in her life. The egg period is about 10 days. The proximate temperature of developmental zero of egg is 9.1 'C. IIatching was observed carefully (Plate 14). The larval period is about 30 days. The full-grown larva begins to spin cocoon one or two days after it stopped to feed. The cocoon seems to be completed within two days, being ellipsoid in shape and brown in colour. The prepupal stage in cocoon lasts about two months. The pupal period is about one month. In one case the transformation to adult stage was observed as early as the middle of September in 1954, but the adults overwintered in the cocoon. 2. Some interesting habits of the female bee were observed. 3. Five natural enemies, viz. Saproglyphus sp. (Acarina) (Fig. 3), Monodontomerus japonicus Ashmead (Hymenoptera, Torymidae), Leucospis japonicus Walker (Hymenoptera, Leucospidae), Ptinus japonicus Reitter (Coleoptera, Ptinidae) and Botrytis sp. (Fungi) were destructive for all but adult stages.