title: Ontogeny of worker body size distribution in bumble bee (Bombus impatiens) colonies.
abstract: Bumble bees exhibit worker size polymorphisms; highly related workers within a colony may vary up to 10-fold in body mass. As size variation is an important life history feature in bumble bees, the distribution of body sizes within the colony and how it fluctuates over the colony cycle were analysed.Ten commercially purchased colonies ofBombus impatiens(Cresson) were reared inad libitumconditions. The size of all workers present and newly emerging workers (callows) was recorded each week.The average size of bumble bee workers did not change with colony age, but variation in body size tended to decrease over time. The average size of callows did not change with population size, but did tend to decrease with colony age. In all measures, there was considerable variation among colonies.Colonies ofB. impatiensusually produced workers with normally distributed body sizes throughout the colony life cycle. Unlike most polymorphic ants, there was no increase in worker body size with colony age or colony size. This provides the first, quantitative data on the ontogeny of bumble bee worker size distribution. The potential adaptive significance of this size variation is discussed.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, U.S.A. ; Laboratory of Apiculture and Social Insects, Department of Biological and Environmental Science, University of Sussex, Falmer, Brighton, U.K.
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Couvillon
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, U.S.A.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Jandt
authors.affiliation: Center for Insect Science, University of Arizona, Tucson, Arizona, U.S.A.
authors.forename: Nhi
authors.initials: N
authors.lastname: Duong
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, U.S.A.
authors.forename: Anna
authors.initials: A
authors.lastname: Dornhaus
keywords: Bombus impatiens; bumble bees; polymorphism; size distribution; social insects