Wi BBB: Bombus citrinus

photo of Female on wild bergamot (<em>Monarda fistulosa</em>) — Female on wild bergamot (*Monarda fistulosa*) — Jay Watson

The lemon cuckoo bumble bee is known from eastern U.S. and Canada. Studies have shown declines in Canada, but not in Illinois and eastern U.S. Wisconsin's historic records show it found statewide but most widespread in the southern part of the state. A handful of current observations are spread across the southern half of the state.

The lemon cuckoo is a nest parasite of the common eastern bumble bee (B. impatiens), the twospotted bumble bee (B. bimaculatus), and the half-black bumble bee (B. vagans) (Williams et al. 2014).

Cuckoo bumble bees (subgenus Psithyrus) do not have the ability to collect pollen and thus lay their eggs in the colonies of other species to raise their young (Hatfield et al. 2014). Only new, mated queens overwinter, emerging from diapause (a form of hibernation) in the spring. New queens kill or subdue the queen of a host colony and lay eggs, which the host colony raises. The resulting cuckoo bee offspring are all queens or males. New queens mate and enter diapause.

Status-Global/State:

Global: G4G5 Wisconsin: S3

image showing reference locations of body parts

Identification:

Female – Face intermixed or mostly black and vertex yellow. Thorax mostly yellow with a black spot occasionally. Abdomen color patterns are varied (see photos) T1-2 black or intermixed and T4-5 and T6 black.
Male – Face intermixed or mostly black and vertex yellow. Thorax with black spot or patch. Abdominal segments T1 yellow and T4-T6 black; segments T2-3 either yellow or intermixed especially on the sides.
Other distinguishing features – Abdomen shiny, short cheek/face, and wings are light brown.

Similar Wisconsin Species:

Similar bumble bee species in Wisconsin are the rusty patched bumble bee (B. affinis), confusing bumble bee (B. perplexus), and the half-black bumble bee (B. vagans) (Colla et al. 2011, Williams et al. 2014).

Description of Habitat/Range:

Habitat types are variable, and likely depend on host species. In Illinois, found active in the fall near woodlands (Hatfield 2015)

Nectar Plants

Food plants include Asclepias (milkweeds), Asters, Cirsium (thistles), Eupatorium (Joe-pye weed), Liatris, Pycnanthemum, Rubus (blackberry), Solidago (goldenrods), Trifolium (clovers), Verbena (vervains), and Veronia (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:

The majority of observation records in Wisconsin took place June-September.

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 citrinus. The IUCN Red List of Threatened Species 2014: e.T44937676A68983052.

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.

Female on wild bergamot (Monarda fistulosa) — Jay Watson