Cold-proof cellophane bees face new risks in a warming world

Spring can be messy, but one bee shows up anyway. The cellophane bee is among the first pollinators to rise each year, even while frost still bites. New research reports that this early riser shrugs off cold shocks that would sideline other bees.

Compared to honeybees, it recovers from chill coma about twice as quickly and tolerates much lower temperatures.

Chill coma is when cold knocks an insect into a temporary stupor. Warm it back up, and it can recover – if it’s built for it. Colletes inaequalis, the cellophane bee, is built for it. That edge fits its schedule: adults live only a few weeks in early spring, so every warm hour counts.

Testing bees against spring chills

After collecting wild bees on a Midwestern campus, researchers measured body size, exposed the insects to controlled temperature drops, and timed recovery. They compared males and females, and they stacked the results against honeybees.

“What we wanted to see is how these bees are coping with changes in temperature during the spring,” said study lead author Victor Gonzalez, a professor at the University of Kansas.

He noted that over 75 percent of bees are solitary, but most of what we know about bees comes from studies on social bees like honeybees and bumblebees.

Bees racing spring’s clock

“The cellophane bee is native to North America – a solitary bee that nests in the ground. Most solitary bees have very short lives as adults,” Gonzalez said.

“The species we study lives only four or five weeks. It’s called a cellophane bee because when it makes a nest, it creates cells that look like clear paper, similar to cellophane.”

Adults emerge around spring break and are gone by mid-May. The larvae hatch quickly and become adults, but they remain in the ground until the following year, noted Professor Gonzalez.

Early records from campus bee surveys still matter today. “Sometimes, when they’re flying, it still snows. But spring is coming earlier and becoming warmer. Weather patterns are changing, and we want to know how bees adapt.”

“There are records from the 1980,s from some of Michener’s students, showing that males emerge first from the ground about two weeks before females.”

Cold wins, but heat hurts

Colletes inaequalis can handle cold much better than honeybees – a useful trait for a bee that bets on March and April. Honeybees, however, tolerate heat more effectively, suggesting that warming driven by human activity may place added stress on cellophane bees.

In tests, sex and body size did not affect how well these bees endured temperature extremes; smaller males proved just as hardy as females when the mercury dropped, though repeated blasts of cold slowed recovery.

“These early spring bees pollinate crops and flowers such as apples and blueberries,” Gonzalez said. “However, they are harder to commercialize than honeybees because they’re solitary and ground nesters.”

“They need areas to nest, and unlike honeybees, which have colonies of thousands, solitary bees exist in much smaller numbers. Even so, they’re important for local plants.”

Snowfall starves early bees

Timing is everything for early-emerging males. If flowers lag after a cold snap, survival drops. Gonzalez noted that food impacts survival, while repeated exposures to cold affect their ability to function normally.

“Being exposed to multiple snow days impairs them behaviorally. They can’t recover from these cold events if they’re exposed more than once.”

“This is important because males are emerging from the nests, and if there are several snow days after that with no food, they’re going to die. If they do recover and survive, they may not be able to fly properly.”

A bigger picture for pollinators

Survival is hard work, and the increasingly erratic climate may already be impacting these populations, though more research is needed to assess the effects.

By focusing on a common solitary bee rather than a hive species, the work fills a gap in what we know about pollinators that fly before most others.

It also raises a practical point. Early spring pollination helps set fruit for the year, so understanding which bees can take a cold punch – and which can’t – matters beyond the lab.

The full study was published in the journal Ecology and Evolution.

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