On this beautiful cool Sunday morning, UW Arboretum naturalist Susan Carpenter met the group of 7 Friends who gathered for her Pollinator Tour at the entrance to Picnic Point. She prepared us for our observations of these important pollinators by reviewing the life cycle of a bumble bee colony. I was fascinated by her description of the hardworking queen bumblebee, who emerges in the spring from her solitary underground hibernation, collects nectar from flowers and sets up a nest nearby. Working alone, she lays her first batch of eggs, fertilized in the previous summer, and sits on them to warm them. The queen has to leave the nest to gather more nectar and pollen to feed the hatched larvae which mature into adult female worker bees. As the season progresses, the queen lays unfertilized eggs which develop into haploid males that leave the nest in search of other queens to fertilize. Susan gave each of us a laminated copy of the Bumble Bee Brigade Field Guide to Females and Males of 21 bumblebee species. She also gave us a Rusty Patched Bumble Bee Midwest Plant Guide to native plants that will attract most of the other bumblebee species, too.
We looked for, and found, bees in the rain garden inside the Picnic Point entrance, on the jewelweed opposite Bill’s Woods, and in milkweed in the East Savannah, and then in galore, in the Biocore Prairie. A Tawny emperor butterfly landed on Doris' bike helmet as we entered the prairie, and it stayed there for much of the rest of the tour. Contrary to what one might guess,
Seth, noted, milkweed plants are mostly pollinated by bees, not butterflies. Butterflies prefer to frequent flowers with a kind of a flat surface for landing, like asters or purple coneflowers. Monarchs use milkweeds to lay their eggs, and the Monarch caterpillars feed on milkweed leaves.
Steve was intrigued by the effects that changing climate was having on the bumble bees. The warmer temperatures are forcing the southern boundary of the range north, but there is little opportunity for the bees to disperse farther north, since the queens must begin to form their colonies immediately after they emerge. This means that cooler microclimates within their current range will be vital to conservation and that greater diversity of habitats will be key. As an example, Susan explained about how edges between the woods and prairie are important to the bumble bees.
Susan encouraged us to take our own photos of bees and submit them to the Wisconsin DNR’s Bumble Bee Brigade, wiatri.net/inventory/bbb. As the insects' territory is squeezed by climate change, and they face threats from pesticide use, loss of habitat and disease, the DNR and the Xerces Society can use our observations to guide their bumblebee conservation efforts.
Bumblebees sighted today:
Bombus auricomus black and gold
Bombus bimaculatus twospotted
Bombus griseocollis brownbelted
Bombus impatiens common eastern
Bombus vagans half-black
The federally-listed-as-endangered bee that we were hoping to see, but did not:
Bombus affinis rusty patched
Many thanks to Susan for her very engaging and informative tour. Report by Doris Dubielzig and Friends host Steve Sentoff, Photos by Glenda Denniston, Doris Dubielzig, Seth McGee, Steve Sentoff