A scientific note on the comparison of airborne volatiles produced by commercial bumble bee (Bombus impatiens) and honey bee (Apis mellifera) colonies

Abstract

Investigators have shown (Stanghellini et al. 2000; Spiewok and Newman 2006; Hoffman et al. 2008) that commercial bumble bee (Bombus impatiens Cresson, Hymenoptera: Apidae) colonies can serve as potential alternative hosts for the small hive beetle (SHB, Aethina tumida Murray, Coleoptera: Nitidulidae), a honey bee pest (Lundie 1940; Neumann and Elzen 2004; Ellis and Hepburn 2006). Using olfactory choice tests, Graham et al. (2011) found that SHB attraction to bumble bee colonies is chemically mediated. Since SHBs are attracted to bumble bee and honey bee colonies, we expected the volatile profiles produced by bumble bee and honey bee colony components to be similar. To test this, airborne volatiles produced by bumble bee and honey bee adults, brood (eggs, larvae, and pupae), honey, stored pollen (= bee bread), and wax were collected and analyzed. In June 2007, two commercial bumble bee (B. impatiens) quads (= eight colonies; Koppert Biological Systems, Inc., Romulus, MI) were established at the University of Florida’s Bee Biology Unit in Gainesville, FL (37.629′′29° N, 21.405′′82° W). Both quads consisted of four bumble bee colonies containing a reproductive queen, 200–250 workers, brood, and nesting material. Eight queenright honey bee colonies were housed in typical Langstroth style equipment at the University of Florida’s Bee Biology Unit in Gainesville, FL. Volatiles were collected from colony components using methods modified from Suazo et al. (2003). The colony components (adult bees, brood, honey, pollen, and wax) were extracted from eight bumble bee and eight honey bee colonies. The samples were placed in glass volatile collection chambers (3.8 L) by component and colony at the USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology (CMAVE, Gainesville, FL). All volatile collections were conducted in a controlled environmental chamber maintained without light and at an ambient temperature of ∼33 °C. Charcoal-filtered and humidified air, controlled by carboloy flowmeters, was passed through the volatile collection chambers and into SuperQ filters at a rate of 0.5 L/min. All component volatiles were collected for 14 h with the exception of brood volatiles that were collected for 7 h. The abbreviated time frame for volatile collection of brood was intended to avoid stressing the unattended brood, recognizing the fact that brood may still be stressed in the absence of adult workers. Adult bees were provisioned with a cotton wick saturated with a 50 % sugar water solution and an autoclaved steel mesh platform on which the adults could crawl to minimize stress. Volatiles trapped on the SuperQ filters were extracted by eluting the filter with 500 μL of methylene chloride. These samples were pooled by component and bee type and stored in a −70 °C freezer (Revco Scientific, Inc., Asheville, NC) at CMAVE until use. volatile / Bombus impatiens / bumble bee / Apis mellifera / honey bee / olfaction