Title: A scientific note on Bombus (Psithyrus) insularis invasions of bumble bee nests and honey bee hives in the western United States Authors
Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2014
Publication Date: N/A
Interpretive Summary: Bumble bees are important pollinators of fruit and vegetable crops. One species of bumble bee is parasitic on other bumble bee colonies and can disrupt the colony by invading the nest and killing the rightful queen bumble bee. We observed an outbreak of these parasites in 2012 and report the incidence of nest invasions into bumble bee nests and attempted invasions of honey bee nests. We made behavioral observations of the nest invasion dynamics of the parasites that attempted to invade colonies of honey bees and two species of bumble bees. These are the first reports of this kind in western North America.
Technical Abstract: Bumble bees (genus Bombus) are critical pollinators of flowering plants, yet some species are obligate social parasites that do little pollinating and reduce the fitness of the colonies they invade. In 2012 we observed an outbreak of the parasitic Bombus insularis in the Cache Valley of Northern Utah which provided an opportunity for observations of the invasion dynamics. We observed several colonies of B. huntii and B. bifarius and documented the dynamics of multiple invasions on colony health and reproduction. Colonies invaded by multiple parasites did not reproduce and large numbers of bumble bee workers were killed during invasions, compromising them as pollination units. Additionally, we found large numbers of dead parasites at the entrances of honey bee colonies, indicating that attempting these colonies could be fatal to the parasites.