Bumblebees are important native pollinators in temperate
regions. In North America, we have not paid much interest in them until very recently. The decline of European
honey bees has raised awareness about the ecosystem services pollinators provide. Increasing evidence suggests our native
bees, not only managed honey bees, are critical components in agriculutral systems. Not only do they provide us with
fruits and vegetables, native pollinators have also evolved with native flowering plants and through pollination provide
many wild birds and mammals with food and shelter.
Bumblebees belong to the genus Bombus, in the family Apidae (bees). They are different from other
bees because they are large, fuzzy and carry pollen in 'pollen baskets' on their hind legs. There are approximately
250 species of bumblebee globally and about 50 are found in North America. Bumblebees feed only on pollen and nectar
and thus are not the insects that bother you during picnics. While female bumblebees can sting, they are quite docile
and will only sting if their colony is disturbed or they are cornered.
Bumblebees are eusocial insects. Queen bumblebees emerge in the spring and forage before starting to
lay eggs in a nest (usually underground). When worker bees hatch, they take over the foraging and taking
care of the nest so the queen can focus on producing more eggs. Towards the end of the colony cycle the colony starts
producing males and new queens which leave the colony and mate. The mated new queens go into hibernation for
the winter, while the males, workers and old queens perish. There are a few species of bumblebees which are 'social
parasites'. This means that instead of producing workers, the queen goes into the nest of another species and takes
over. In that nest she produces males and queens of the next generation with the help of the another queen's workers.
Bumblebees are extremely important foragers. Unlike honeybees, they are able to forage
under cold, rainy and cloudy conditions. This makes them excellent pollinators of native plants and a variety of crops.
Some crops which bumblebees can pollinate include tomatoes, peppers, raspberry, blueberry, chives, cucumbers, apples,
strawberries, blackberries, soybeans, sunflower, beans, cherries, eggplants, and cranberries.
We have evidence that in North America some of (not all) our bumblebee species
are in decline. In fact, one species known from Oregon and California (Franklin's Bumblebee) has recently been listed
by the IUCN as Critically Endangered. The Rusty-patched Bumblebee has only been located at a handful of site in recent
years and is listed as Endangered in Canada. Scientists are quickly trying to figure out what is causing these declines
so we can start conserving what we have left. Currently, the suspected threats to wild bumblebees are:
1) Habitat loss (i.e.places to nest and the right flowers to feed from)
2) Pesticide use
3) Pathogen Spillover
from managed bees
4) Climate change
5) Introduced Species
Happy Bumblebee-watching! Sheila Colla, PhD