Where Do Native Bees Go In Winter?
Excerpted from: Bees & Bloom
Ever wondered where native bees go in the winter?
There are many different strategies for surviving the cold
months! We’ll take a look at the winter survival strategies of native bumblebees, and
Understanding the habitat requirements of Wisconsin's native bees will be of utmost importance since, as
we now know, promoting bee species diversity is critical as native bees are needed for effective pollination
of both crops and wild plants and they are under decline.
Bumble Bee queens hibernate in winter.
Most solitary bee species will overwinter in a birth cell, either as new, fully developed adults
not yet emerged from their cells, or as pupae, waiting to complete their development.
Non-native honey bees overwinter in their hive or nest, forming a winter cluster around the queen, with
the colony itself much reduced in size. They are less active though not entirely dormant,
and the cluster 'shivers' to keep warm.
In Wisconsin's cold climate, where there are no flowers from which to feed in the winter,
bees need to shelter from the weather and conserve their energy until the flowers are blooming again.
Dead plant stems, bark, cane, leaves and especially undisturbed soil are the secret winter homes of
Wisconsin's solitary bees.
Exposed Bumblebee Nest
Bumblebees are the only colony-dwelling bees in Wisconsin. The species in this genus have their best shot for
survival by being annuals. As autumn approaches, fewer species of bumblebee are seen foraging. The
natural lifecycle of bumblebees means that most of the colony will die, and only the new bumblebee queens will
survive. They will mate with the males, and importantly, feed to build up fat reserves ready for their winter
snooze (hibernation). The mated queens will hibernate through the winter underground as the only surviving
individuals from their parent colony.
The lucky queens who hibernate successfully without disturbance will emerge from their burrows when spring
temperatures signal it is time for them to start a colony of their own. The season of the queen begins with
searching for an optimal nesting site while visiting flowers to sip nectar for energy. Nesting sites for bumblebees
are scarce, and even if a queen finds a suitable site, the chances that she starts a successful colony are slim!
Overwintering Adult Bumblebee
After locating a suitable site, she must play both queen and worker, starting the risky business of leaving the
nest untended in order to forage for the few young she can produce on her own. If a queen makes it past this
stage, she can stay inside the nest and focus on laying eggs while her daughters (the workers) take care of the
rest of the work until winter rears its cruel head once more.
Are changes in climate affecting hibernating patterns of bumblebees - such that we even witness winter active
bumblebees? In milder climates – and even in milder weather zones of countries such as the UK, bumblebees
have been known to remain active through the winter. If winters are getting warmer, perhaps this should not
Solitary Leafcutter Bee
Returning To Nest
Most bees in Wisconsin are solitary. During the warm season, a single, mated female will tend a nest in a
tunnel. Depending on the species, the tunnel may be in a network underground, or in an abandoned hole off the
ground left behind by beetles, woodpeckers, or even humans (check it out!).
The female solitary native bee will work through an active
season, a bit over a month, until her death, leaving behind several offspring with enough food to help them
develop properly through the rest of the warm season
Depending on the timing of the adult’s active season, the young left behind will overwinter as fully formed adults
in their cocoons, or as diapause larvae, waiting to pupate until spring.
Bees active in earlier spring, like Mason Bees, will have ample time to pupate in the summer and will overwinter
as hibernating adults in their cocoons. The young left behind by bees active in the summer, like Leafcutter Bees,
will have less time to develop, and will overwinter as hibernating larvae.
Either way, these bees will emerge out of their burrows at the same active time as their parents the year before
and will begin the process again.
Some solitary bees are very tiny and may overwinter in hollow plant stems – something you should be aware of!
As you begin to tidy up your garden for the winter - especially if they are thinking of burning or removing
the plant stems, you may be destroying solitary bee nests.
If you are one of those gardeners who has felt inferior to your neighbors who fastidiously clean up every shred
of plant debris and till the soil in November to be ready for spring, it’s time to stand tall and proud for having a
Dead plant stems, old bark, cane, leaves and especially undisturbed soil are the secret winter homes of
pollinators. Some have gorged like bears to make it through the winter; others wait in suspended animation as
larvae, pupae or eggs.
So, now that you know how many species are counting on you to leave soil undisturbed, piles of leaves
untouched, and shrubbery unpruned over winter, you can feel good about being the untidy gardener! And if
you’d like to fashion some homes for bees, that’s entirely possible.
Here’s a website that provides several different plans for do-it-yourself native bee habitat,
Creating Solitary Bee Habitat
that works well for native bees. A myriad of others are available; to see their diversity and artistry, check out
“native pollinator houses” and click on “images”. It’s also possible to make butterfly and bat houses, and winter
is a great time for woodworking projects!