Colony Development of Two Species of Japanese Bumblebees Bombus (Bombus) ignitus and Bombus (Bombus) hypocrita Reared under Artificial Condition (Hymenoptera, Apidae)

Colony development of two species of Japanese bumblebees was studied in artificial nesting boxes. A Total of 77 queens of Bombus ignitus and 14 queens of B. hypocrita were collected and prisoned in 50 small wooden boxes. Four out of 42 queens (9.5%) in B. ignitus and one out of 8 queens in B. hypocrita (12.5%) developed into normal colonies. The mean number with standard deviation of workers, males and new queens produced per colony was 191.3±40.0, 138.0±52.1 and 26.3±19.5 in B. ignitus (N=4) ; 94, 255 and 12 in B. hypocrita (N=1), respectively. The cause of the lower ratio of normally developed colony should be due to that almost all of the colonies switched early into male producing phase. Differing from B. terrestris, mother queens of B. ignitus continued to lay diploid eggs to a certain ratio even after the switch point.