Bumble Bees of Montana
Bombus (Cullumanobombus) griseocollis (DeGeer, 1773) Brown-Belted Bumble Bee
Bombus griseocollis is one of the most widespread and abundant species in the eastern U.S. temperate forests and Great Plains and is known from lower elevations in the Rocky Mountains (Williams et al. 2014). It is common in Montana, especially east of the continental divide.
Bombus griseocollis is one of four Montana species (along with B. rufocinctus, B. nevadensis, and B. auricomus) in which males have eyes that are greatly enlarged. The enlarged eyes are associated with territorial behaviors connected to mating in these species (O’Neill et al. 1991).
Bombus griseocollis has a cheek that is shorter than it is wide. The top of the thorax is predominately yellow with only a small circle of black hairs between the wings. Abdominal T1 has yellow hairs, T2 can have yellow or brown hairs and may have black hairs on the side, and T3-T6 are all entirely black. The exoskeleton beneath the hairs on T1 and T2 is dull and matte-looking.
This species is most easily confused with B. rufocinctus. However, B. rufocinctus has many black hairs between the wings, usually forming a band of black hairs. Also, the exoskeleton beneath the hairs of T1 and T2 is shiny in B. rufocinctus and there usually is at least some yellow or orange hairs on T3, T4, T5 or T6.