Yellow Cuckoo Bumble Bee, Bombus citrinus
Excerpted from Bumble Bees of Wisconsin
The lemon cuckoo is a nest parasite of the common Eastern Bumble Bee, the Two-spotted
Bumble Bee and the Half-black Bumble Bee. The cuckoo bee locates a host nest by trailing
chemical signatures left by host workers. After locating a host nest the cuckoo will revisit to
further observe the nest and will proceed to infiltrate if she determines the nest to be suitable
for a successful usurping.
Like all cuckoo bumble bees, the outer tibial surface of the hind leg is convex and densely hairy,
rather than adapted for pollen transport. Their heads are more tear-drop shaped and the thorax is
predominantly yellow including the lower sides. Hair on the face is usually black with some yellow
hairs, there are usually no black hairs on the thorax and would not form a band between the wing
bases. The wings are slightly opaque ranging from a reddish brown to brownish black and yellowish
during pubescence. They are sometimes interspersed with black hairs.
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.
The majority of observation records in Wisconsin took place June to September.
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.
Cuckoo bumble bees 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).
Slo-Mo Footage of a Bumble Bee Dislodging Pollen
Look Inside a Bumblebee Nest
How to Build a Bumble Bee House
Development of Colony and Nest in the Bumblebee