Laboratory-reared colonies of Western bumblebee Bombus occidentalis allowed to forage freely produce as many workers as captive colonies on agricultural land at Pitt Meadows, British Columbia, Canada

Published source details

Whittington R. & Winston M.L. (2004) Comparison and examination of Bombus occidentalis and Bombus impatiens (Hymenoptera: Apidae) in tomato greenhouses. Journal of Economic Entomology, 97, 1384-1389.

Background

The Western bumblebee Bombus occidentalis has declined dramatically in North America. Re-introducing captive-bred colonies is one possible conservation response. This study examined the productivity of laboratory-reared colonies allowed to forage in agricultural land and woodlands at Pitt Meadows, British Columbia, Canada.

Action

In early May 2001, seven 12-week old commercially produced colonies of B. occidentalis were placed outside in wooden boxes provided with sugar syrup. Seven similar colonies were placed inside a 2.5 ha greenhouse at the same site. The indoor boxes were screened, so bees could not leave or enter the hive and provided with sugar syrup, water, and pollen collected by honey bees Apis mellifera, mixed with 50% honey:water solution. Water and pollen were replaced weekly.

The numbers of queens, males, workers, egg masses, larval masses, pupae and honey/pollen pots were counted in each colony (under red light to minimise disturbance) at the start of the experiment and every week for eight weeks.

Consequences

There was no significant difference between enclosed and outside colonies in the number of workers per hive throughout the experiment (average between 40 and 90 workers/hive).

Enclosed colonies had significantly lower amounts of brood than outside colonies. After eight weeks, outside colonies had an average of around 80 eggs, larval masses and pupae, compared to an average of less than 40 for enclosed colonies. These results reflect greater adult bee mortality in the outside environment.

Five weeks into the experiment, honey bees began to rob sugar syrup from the outside colonies, resulting in high bumblebee mortality (no numbers given).

Note: If using or referring to this published study, please read and quote the original paper, the abstract of which can be viewed at: http://www.entsoc.org/pubs/periodicals/jee/