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Division of Labour and Foraging in Bombus agrorum Fabricius

Anne D. Brian
Journal of Animal Ecology
Vol. 21, No. 2 (Nov., 1952), pp. 223-240
DOI: 10.2307/1959
Stable URL: http://www.jstor.org/stable/1959
Page Count: 18
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Division of Labour and Foraging in Bombus agrorum Fabricius
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Abstract

1. The behaviour of workers marked individually has been studied in four observation nests of B. agrorum. 2. Both large and small workers foraged and undertook house duties; the apparent division of labour previously noted results from the later age at which small workers begin to forage, about 15 days from emergence as against 5 days for the large workers. 3. By manipulation of colonies it was found that neither absence of foraging bees nor absence of nectar caused the small house-bees to begin foraging. It was therefore considered to be a matter of ontogeny. 4. The longevity of the workers was variable, 69 days being the maximum recorded. On the average 29% of the bees died every 5 days. House-bees lived slightly longer than foragers, particularly in a bad season. 5. About two-thirds of the total bee population were house-bees and one-third foragers at any particular time. 6. No trend in duties with age was observed in the house-bees, foragers, when in the nest, performing a variety of house duties. 7. The larger foragers collected pollen and nectar, 75% of pollen loads being accompanied by nectar. The smaller foragers tended to collect nectar only. 8. In all, 665 foraging trips were timed, the averages for two nests being 17.5 and 15.3 min. Pollen loads with or without nectar took longer to collect than nectar loads alone and loads were collected faster in damp weather than in dry. 9. Pollen loads from one nest were collected and identified. Out of 120 loads, sixty-seven were mixtures of from two to six plant species. The pollen collection of individual workers indicated moderately fixed foraging habits. 10. Normally the workers behaved indifferently towards each other but on a very few occasions attacks were observed in which the attacked bee was forced to disgorge liquid or leave the nest. The attacker was always a house-bee, the attacked a forager. A comparison with the dominance order in Polistes wasps is made.

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