Providing evidence to improve practice

Individual study: Buff-tailed bumblebee Bombus terrestris queens bred in captivity become lighter over successive generations; laboratory studies at the University of Amsterdam, Noord Holland, the Netherlands

Published source details

Beekman M., Van Stratum P. & Lingeman R. (2000) Artificial rearing of bumble bees Bombus terrestris selects against heavy queens. Journal of Apicultural Research, 39, 61-65

Background

Bumblebees Bombus spp. are declining in Europe and America, and captive rearing could be used to augment or re-establish populations. Previous studies have shown that queen buff-tailed bumblebees B. terrestris weighing less than 0.6 g do not survive hibernation. This study measures the weight of laboratory-reared B. terrestris queens over successive generations at the University of Amsterdam, The Netherlands.

Action

Starting in October 1993 with 47 queens reared from wild-caught queens, successive generations of B. terrestris were reared in the laboratory, with one to three generations per calendar year until July 1996. 170 colonies were reared altogether.

For each generation, newly emerged queens were placed in a mating cage with newly emerged males, then in a flight cage for one week before being weighed. 2,210 queens were weighed overall.
 
Queens were hibernated for two to four months in the laboratory, and induced to form colonies by confinement with two to four honey bee Apis mellifera workers. Colonies were kept at 29° C and 62% relative humidity, and regularly provided with sugar syrup and fresh pollen collected by honey bees. The number of queens produced by each colony was counted.
 
In 1996, five generations of brother-sister matings were reared. For this study, egg-laying was induced with carbon dioxide treatment, and the hibernation stage omitted.

Consequences

The average weight of outbred queens decreased linearly over time, from 0.83 g in 1993 to 0.73 g in 1996. Queens weighing over 1 g were present in 1993, infrequent in 1994 and absent in 1995 and 1996.

The number of queens per colony was not significantly different between years, with the average number of queens/colony ranging from 59-76.
 
After five generations of inbreeding in the 1996 study, the average weight of queens did not decrease.
 
The authors suggest that the observed decrease in queen weight over four years is due to an unknown nutrient deficiency in the diet.
 
 
Note: If using or referring to this published study, please read and quote the original paper, which is available through the International Bee Research Association http://www.ibra.org.uk