Wi BBB: Bombus ternarius

photo of Male on Joe Pye weed (<em>Eupatorium maculatum</em>) — Male on Joe Pye weed (*Eupatorium maculatum*) — Jay Watson

The tricolored bumble bee is known from the northern U.S. and southern Canada and populations appear to be stable (Hatfield et al. 2014). Wisconsin has recent observation records from the northern and central counties. Older records are found scattered throughout the state, but most abundant in the northern and central part of the state.

The indiscriminate cuckoo bumble bee (B. insularis) is a likely nest parasite of the tricolored (Williams et al. 2014).

The tricolored bumble bee, like other bumble bees, live in colonies composed of a single queen and female workers. Colonies start to produce new queens and males in the mid- to late summer. Only new, mated queens overwinter, emerging from diapause (a form of hibernation) in the spring. New queens are responsible for finding a new nest site, laying eggs, and for all of the foraging and care of the colony until the first workers emerge (Hatfield et al. 2014). Once the first workers emerge, the queen remains in the colony laying eggs. Bumble bees need areas that provide nectar and pollen from flowers throughout the duration of the colony life cycle, and suitable sites for nesting and for overwintering queens.

Status-Global/State:

Global: G5 Wisconsin: S4

image showing reference locations of body parts

Identification:

Worker – Face and vertex yellow or intermixed. Thorax mostly yellow with a triangular shaped black band between the wingpads that points towards the abdomen. Abdominal segment T1 yellow, T2-3 orange, T4 yellow, and T5-6 black.
Queen/gyne – Similar to workers, but are larger and appear earlier in the season.
Male – Face and vertex yellow. Thorax mostly yellow with black band between the wingpads. Abdominal segment T1 yellow, T2-3 orange, T4 yellow, and T5-T7 either black, yellow, or a combination.
Other distinguishing features – Hair short and even.

Similar Wisconsin Species:

Similar bumble bee species in Wisconsin are the red morph of the redbelted bumble bee (B. rufocinctus) (Colla et al. 2011).

Description of Habitat/Range:

Known habitats include wooded and wetland areas (Williams et al. 2014). Nests have been found mostly underground (Colla et al. 2011, Williams et al. 2014).

Nectar Plants

The tricolored bumble bee is a medium-tongued species (Williams et al. 2014). Nectar plants include Asclepias (milkweeds), Claytonia, Eupatorium (Joe-pye weed), Rhododendron, Rubus (blackberry), Solidago (goldenrods), Symphyotrichum, Taraxacum (dandelion), Trifolium (clovers), and Vaccinium (blueberry) (Williams et al. 2014, Colla et al. 2011).

Click on the legend symbols for each type of bumble bee to add or remove them from the graph.
Data from verified B3 observations [updated 2/28/2024].

Flight Season:

In Wisconsin, observation records have been made in May through October. Range-wide, queens start emerging in April and enter diapause by September (Colla et al. 2011).

Literature Cited:

Colla, S., Richardson, L. and Williams, P. (2011) Bumble Bees of the Eastern United States. A product of the USDA Forest Service and the Pollinator Partnership with funding from the National Fish and Wildlife Foundation.

Hatfield, R., Jepsen, S., Thorp, R., Richardson, L. & Colla, S. 2014. Bombus ternarius. The IUCN Red List of Threatened Species 2014: e.T44937988A69005644.

Williams, P.H., Thorp, R.W., Richardson, L.L. and Colla, S.R. (2014) The Bumble bees of North America: An Identification guide. Princeton University Press, Princeton.

Male on Joe Pye weed (Eupatorium maculatum) — Jay Watson