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Montana Field Guide

Montana Field Guides

Half-black Bumble Bee - Bombus vagans
Other Names:  Pyrobombus vagans


Global Rank: G5
State Rank: SNR

Agency Status
USFWS:
USFS:
BLM:


 

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General Description
For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page. A long-tongued medium-sized species: queens 17-21 mm in length, workers 11-14 mm. Hair medium, head length medium with cheek just longer than wide; mid-leg basitarsus with back far corner rounded, hind-leg tibia outer surface flat and lacking long hair (except fringe), pollen basket present; hair of face black; upperside of head (occiput) yellow especially centrally; upper surface of thorax yellow with a central black dot between wings, sides of thorax entirely yellow; T2 mostly yellow at front, sometimes black along back; T3-4 and S3-5 usually black at the sides unless T3-4 black on upper surface. Male 11-14 mm in length; eyes similar in size and shape to eyes of any female Bombus; antennae medium length, flagellum 3X longer than scape; hair of face yellow with black intermixed at least around base of antennae; upper surface of thorax predominantly yellow; T3 usually black in the middle, T5-6 often yellow at the sides (Colla et al. 2011, Koch et al. 2012, Williams et al. 2014).

Phenology
Across the range, queens reported April to October, workers May to November, males May to November (Colla et al. 2011, Williams et al. 2014). In eastern Washington, queens reported April to July, workers May to November, males July to November (Koch et al. 2012).

Diagnostic Characteristics
Please see the Montana State Entomology Collection's Key to Female Bumble Bees in Montana. Females told from other Montana Bombus by a combination of hind-leg tibia outer surface concave and hairless (except or fringe), pollen basket present; cheek longer than wide; face predominantly with black hairs; T2 yellow, T3 mostly black, T4-6 black; sides of thorax predominantly yellow.

Species Range
Resident Year Round

Recorded Montana Distribution

Click the map for additional distribution information.
Distributional Information Provided in Collaboration with the
Montana Entomology Collection at Montana State University
MTEC at MSU

 


Range Comments
Central and northeastern US and adjacent southern Canada west to eastern Washington, northern Alberta and British Columbia, with scattered records south in the Rocky Mountains to central Colorado (Williams et al. 2014). Experiencing moderate declines in range and abundance in the east (Colla and Packer 2008, Colla et al. 2012).

Habitat
Forests, wetlands, urban parks and gardens, tall grass prairie, irrigated prairie and woodland riparian, prairie parkland, foothill grassland-forest ecotone (Hobbs 1967, Hines and Hendrix 2005, Grixti et al. 2009, Williams et al. 2014).
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habit Model available.

To learn how these Models were created see http://mtnhp.org/models

Food Habits
Feeds on a wide variety of plants (more than 60 genera), including Arctium, Asclepias, Berberis, Chelone, Cirsium, Claytonia, Geranium, Helianthus, Hydrophyllum, Impatiens, Lonicera, Mertensia, Monarda, Penstemon, Phlox, Polymonium, Prunella, Prunus, Ribes, Sisyrinchium, Scrophularia, Solidago, Spirea, Syringa, Taraxacum, Trifolium, Vaccinium, Vicia, and Viola (Mayer et al. 2000, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014).

Reproductive Characteristics
Nests built mostly underground, although occasionally on the surface or above ground (Hobbs 1967, Colla et al. 2011, Williams et al. 2014). In southern Alberta, nests established mid to late June; mean number of pupae in first broods is 8-10 (Hobbs 1967). Males patrol circuits in search of queens. Nests sometimes parasitized by the cuckoo bumble bee Bombus citrinus.

References
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Citation for data on this website:
Half-black Bumble Bee — Bombus vagans.  Montana Field Guide.  .  Retrieved on , from