Observations of successful Bombus terrestris (L.) (Hymenoptera: Apidae) colonies in southern Tasmania

Early attempts to acclimatise Bombus spp. to Australia were not successful but a pre-1992 introduction of the bumble bee B. terrestris has succeeded and the species is slowly spreading in southern Tasmania. It is likely that the genetic base of the Tasmanian population is limited if, as is thought, only a few queens were brought from New Zealand. This may affect the rate of dispersal through the island, which presently averages 12.5 km/year. In 1995-96 Is feral colonies found in and around Hobart were transferred to nest boxes, where colony development could be monitored. All of the colonies produced queens, and the ratio of queens to workers (1:4.71) compares favourably with the upper end of colony performance scale in New Zealand(1:5.19). At least two generations are produced during warmer months and there is no indication of genetic impediments to further dispersal in Tasmania or possibly even mainland Australia. External influences such as predatory habits of birds, availability of food, competition from other insects and deliberate introduction by people into new areas make the rate of spread unpredictable.