Cuckoo Bumble Bees — Social Parasites
Ashton's Cuckoo Bumble Bee
A Cuckoo Bumble Bee, like the bird it is named after, lays its eggs in another bumble bee’s nest
and leaves the workers of that nest to rear the young. The eggs she lays are either females or
males — there are no queens.
The cuckoo females emerge from hibernation in late spring or early summer, much later than
ordinary bumblebee queens. So by the time the cuckoo females have emerged the bumble bee
queens will have already established their nests.
One key to their success as bumble bee parasites is that they usually have the same patterns of
color as the bumble bee whose nest they lay their eggs in.
In Wisconsin, there are 2 native cuckoo bumble bee species, both of which are very rare, the
Ashton Cuckoo Bumble Bee
and the Yellow Cuckoo Bumble Bee.
Entomologists refer to cuckoo bees as kleptoparasites due to the nature of procreation.
Unlike other bee species, cuckoo bumble bees do not take care of their own young. Instead, they trick
their host species to do it for them through deception and sneaky tactics.
The cuckoo has evolved a number of characteristics, which mean it is totally reliant upon its
host for its future survival.
Cuckoo bees are notoriously hard to detect. Since they are usually related to their host, the
similarities in appearance make it really difficult to tell them apart. They instinctively lurk
around the host’s colony to take on their odor. Masking their presence with both colors and
chemicals makes infiltrating the nest a lot easier.
Because they need to move behind enemy lies, cuckoo bees are a bit bigger and a lot tougher
than their host. Some species infiltrate and kill the host queen, which means they need to be
bigger, have stronger mandibles, and harder exoskeletons.
First, cuckoo species are unable to establish their own nests. They do NOT have the ability to
excrete wax from their abdomens for making egg cells in which to lay their eggs, nor can they
make honey pots from which newly emerged brood may feed, and from which they may feed
themselves whilst they incubate the brood. The cuckoo female must use the larval cells and
cups made by the host queen.
The cuckoo female also cannot collect pollen for returning to her nest, since she has no pollen
baskets (corbicula) on the hind legs, although they do of course, eat pollen, just
as social bumble bees do. Pollen is important as it helps the ovaries to mature in the fertilized
females, and it is used for feeding the brood.
Also, cuckoos are unable to rear workers. The cuckoo merely lays females and males like herself,
and these offspring are likewise limited, in that they cannot perform the tasks that worker bees
of the social species can undertake, in order to sustain the colony such as building wax cells and
Cuckoo females typically emerge from hibernation a few weeks after the target host species. Some
cuckoos target only one specific species of bumble bee, whilst others may select from 2 or 4 target
The queen cuckoo bumble bee must first locate a ready prepared nest at an appropriate stage of
development. Female cuckoo must choose her target host carefully. There must be a colony already
established of at least a few workers to help the cuckoo rear her offspring. On the other hand, if there
are too many workers in the nest, she may be attacked and easily defeated.
A nest with 2 broods already reared, may have enough workers to overpower the cuckoo, and prevent
her establishing herself in the nest.
Once the cuckoo has found a suitable nest, she will typically lurk around it for some time, in order to
‘pick up the scent’ of the host. This will help her to usurp the resident queen if necessary, and gain
acceptance of the workers through physical attacks and the use of her pheromones.
Once the cuckoo enters the nest, there are a variety of scenarios that may occur, but a common one
is that the original host queen is killed. The cuckoo will then set about laying her own eggs in the nest
for the workers of the original queen to tend to and feed.
Timing is critical. If the cuckoo has entered a nest that is well developed, and there are many workers,
they may attack the parasite, and kill her. On the other hand, if there are too few workers to support her,
then she will not be able to rear many offspring.
Very often, she will be. Although cuckoos closely resemble social species, the female parasite is
often a little larger than her host. She has a more powerful, longer sting, and a thicker, though less
hairy coat. She can often overpower the founder queen unless there are sufficient workers to attack her.
However, there have been reports of both host and cuckoo cohabiting in a nest for quite some time,
with the cuckoo even incubating the host queen eggs, and offspring from both the cuckoo and host
Plants had to solve a problem: they needed to find ways to spread their genetic material.
Flying pollinators were nature's solution. Nectar is made as a reward for pollinators.
Take this quick quiz and see how much you know about bees—our favorite essential pollinators
working around the world. This quiz is intended for fun, in a random-facts-can-be-cool kind of way.
Have you ever wondered how bees fly and why is there all that buzzing? Buzzing is the sound of
a bee’s beating wings. Scientists first realized that bees seem to flout the laws of mathematics
in the 1930s.