Bumble Bees (Hymenoptera: Apidae: Bombus spp.) of Interior Alaska: Species Composition, Distribution, Seasonal Biology, and Parasites.

Background: Despite the ecological and agricultural significance of bumble bees in Alaska, very little is known and published about this important group at the regional level. The objectives of this study were to provide baseline data on species composition, distribution, seasonal biology, and parasites of the genus Bombus at three major agricultural locations within Alaska: Fairbanks, Delta Junction, and Palmer, to lay the groundwork for future research on bumble bee pollination in Alaska.

New Information: A total of 8,250 bumble bees representing 18 species was collected from agricultural settings near Delta Junction, Fairbanks, and Palmer, Alaska in 2009 and 2010. Of the 8,250 specimens, 51% were queens, 32.7% were workers, and 16.2% were males. The species composition and relative abundances varied among sites and years. Delta Junction had the highest relative abundance of bumble bees, representing 51.6% of the specimens collected; the other two locations, Fairbanks and Palmer represented 26.5% and 21.8% of the overall catch respectively. The species collected were: BombusbohemicusSeidl 1837 (= B.ashtoni (Cresson 1864)), B.balteatusDahlbom 1832, B.bifariusCresson 1878, B.centralisCresson 1864, B.cryptarum (Fabricius 1775) (=B.moderatusCresson 1863), B.distinguendusMorawitz 1869, B.flavidusEversmann 1852 (=B.fernaldaeFranklin 1911), B.flavifronsCresson 1863, B.frigidusSmith 1854, B.insularis (Smith 1861), B.jonellus (Kirby 1802), B.melanopygusNylander 1848, B.mixtusCresson 1878, B.neoboreusSladen 1919, B.occidentalisGreene 1858, B.perplexusCresson 1863, B.rufocinctusCresson 1863, and B.sylvicolaKirby 1837. Overall, the most common bumble bees near agricultural lands were B.centralis, B.frigidus, B.jonellus, B.melanopygus, B.mixtus, and B.occidentalis. Species' relative population densities and local diversity were highly variable from year to year. Bombusoccidentalis, believed to be in decline in the Pacific Northwest states, represented 10.4% of the overall specimens collected from the three sites studied. Bumble bees were found to be infected by Nosema and nematodes with infection rates up to 2.1% and 16.7% respectively. Of the eight species infected by parasites, B.occidentalis displayed the highest Nosema infection, while B.centralis was the species with the highest infection of nematodes. To our knowledge this represents the first multi-year study on bumble bees from the main agricultural areas of Alaska to provide baseline data on species composition, distribution, seasonal biology, and parasites of the genus Bombus.