Researchers to conduct first survey of Minnesota's native bees

Trapping bees
Plastic cups are painted and filled with soapy water to attract and trap bees at Otter Tail Prairie Scientific and Natural Area near Fergus Falls.
Dan Gunderson/MPR News

A few miles west of Fergus Falls, dew on the prairie grass sparkles in the morning sun, as Crystal Boyd, an entomologist for the state Department of Natural Resources walks into the Otter Tail Prairie Science and Natural Area.

Among the yellow and purple prairie flowers is a row of 12 plastic cups suspended on poles about the same height as the plants — an ideal setting for researchers who need to capture bees.

For years, scientists have studied honeybees to assess the connection between their declining population and the use of pesticides, declining habitat and disease. But until recently, they paid little attention to Minnesota's native bees.

This summer DNR researchers are traveling the length of western Minnesota to conduct the first population survey of native bees. That's where the cups come in. They are filled with soapy water to trap insects, which Boyd said is an unfortunately necessary technique, as the only way to count insect populations is to kill them.

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"These cups are painted with a UV florescent paint and the bees are attracted to the yellows, the blues and the whites," said Boyd, who is leading the statewide bee survey. "Those are their favorite colors."

Researchers will collect the insects from each cup to identify them later. Big fuzzy bumble bees are easy. But many native bees are the size of a grain of rice and live inside plants and Boyd will need a microscope to identify them.

Minnesota has a list of native bees, but it was written in 1919 and is missing many of the state's more than 350 different species of native bees.

Entomologist Crystal Boyd collects insects.
DNR entomologist Crystal Boyd collects the insects trapped in a cup of soapy water on the Otter Tail Prairie Scenic and Natural Area.
Dan Gunderson/MPR News

The research project, funded by a $370,000 grant from the Environment and Natural Resources Trust Fund through state lottery proceeds, will allow scientists to create a new list over the next two years.

Although historically researchers have found it difficult to obtain funding for bee research, that's changing because of growing public interest in pollinating insects, Boyd said. Typically the focus is on honeybees because of their importance to many crops. But native bees are busy too.

"Our native bees are incredibly important pollinators," she said. "They're supporting our prairie ecosystem, creating habitat and food for wildlife. They're pollinating plants that prevent soil erosion, that buffer waterways, that store carbon. They were pollinating plants in Minnesota before honeybees even arrived."

Among the plants that depend on bumblebees for pollination are the tomato plants in many backyards.

Researchers think at least three of 18 bumblebee species — the most studied of native bee species — are in trouble. But they have far more questions than answers.

"It's really hard to say what native bee populations are doing in Minnesota right now," Boyd said. "Bumblebees are a little easier. They're easier to see [and] more people have collected them so we have more data. Anything smaller than a bumblebee, we really don't know."

The bee survey will continue through October as researchers visit 90 sites every two weeks to make sure they capture bees that are active during different times of the summer.

A collection of insects taken from 24 traps.
A collection of insects taken from 24 traps on the Otter Tail Prairie Scenic and Natural Area July 30th 2014.
Dan Gunderson/MPR News

They also will analyze the historical record found in insect collections at institutions like the University of Minnesota to get a better idea of past bee diversity in the state.

So far, Boyd is finding fewer bees than she expected. She suspects a cold wet spring might have reduced bee numbers.

Her research is only a first step in learning about native bees. Scientists may need up to 20 years of population data to establish trends.

Although this year's will provide a snapshot of bee diversity in the state, it won't tell scientists if native bees are in decline.

"It would help us to see if species are moving in or disappearing from Minnesota," Boyd said. "If we don't track what we have we don't know if we're gaining new bees or losing what we have."