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Researchers have sights set on bees' feeding habits

 Researchers have sights set on bees' feeding habits

If there’s one thing Lisa Horth and her ODU students have learned, it’s that size does matter.

Working with bees – all kinds of bees – and a yellow flower called a black-eyed susan, Horth has been studying the shapes and colors that bees see.

To a human, the petals of a black-eyed susan look yellow. To a bee, there’s a big bull’s-eye around the center that is visible only in ultraviolet light. Humans can’t see ultraviolet. the bull’s-eye acts as a target, pointing the bees to food, and at the same time luring them into spreading pollen from one plant to another.

On the campus of Norfolk’s Old Dominion University, on the grounds of the Virginia Zoo and at Colorado’s Rocky Mountain Biological Station, Horth and her students are showing that bees prefer plants with large ultraviolet targets – the bigger, the better.

Now she’s hoping it matters enough to land the research in the journals Science or Nature.

That would be the bee’s knees.


Horth has been studying the ultraviolet preferences of bees for two years, using wild and cultivated plants. What she learns could have global significance – bees pollinate many plants, enabling them to produce seeds or fruit.

But bees are getting scarce, which threatens the agricultural industry and the food supply. Horth’s research is looking for answers to many questions: Do the remaining bees prefer plants with larger ultraviolet targets? Do wild plants have naturally larger ultraviolet targets than cultivated ones? when humans cultivate plants to look prettier in our eyes, do we inadvertently make them less attractive to bees? is there a way to make the most important plants more attractive to pollinators? Do larger ultraviolet targets, called cues, provide more pollen?

"Bee abundance is declining," she said. "It’s important to know what the bees prefer."

With scissors and Elmer’s glue, the biology professor and her students are trying to find out.

"Bee on!" said senior Lindsie Abbott.

On a hot, humid day in September, Abbott and two other students sat in the grass at the Virginia Zoo, intently watching a row of black-eyed susans whose cut stems were stuck into water-filled glass soda bottles.

Using plants cultivated for home gardens, the students had cut and glued the petals in three different formations.

One flower had all the ultraviolet targets covered. another had an ultraviolet spot larger than normal. the third had petals cut and glued in the normal pattern of ultraviolet cues to eliminate cutting and gluing as a bias.

The students set up next to three honeybee hives, and waited. Abbott comes every day, for several hours each time, to see whether bees have a preference and to time how long each bee spends on each susan.

Although it has been known for many years that bees see ultraviolet light, and that plants have ultraviolet targets, many questions remain, Horth said.

"No one has done any manipulations like this," she said. "this takes our knowledge about natural preferences and insects several steps further than has previously been known."

Next to the beehives are several small greenhouses, each screened with black netting that blocks a certain percentage of ultraviolet light from reaching the plants inside. Horth and her students are measuring the effect of that blockage on the plants, to see if global climate change and ozone holes affect the ultraviolet targets.

"We do see differences in temperature between the two parts of the petal – the UV cue and the non-UV cue," Horth said. "if we continue to create holes in the ozone, are we affecting what grows on Earth?"

To help answer such big questions, Horth drank a whole lot of Jones soda in a very short time.

The empty soda bottles are identical, so the bees’ preference is not affected by the container. Emptying all those bottles took a while, but watching bees can be slow work, too – the most bees Abbott has seen in a three-hour shift is 11 on the susans, and most of those were sweat bees.

In this case, size doesn’t matter; the tiny bees that are attracted to sweat are still important pollinators, especially on alfalfa and blueberries, Horth said. Black-eyed susans are related to sunflowers, a major oil crop.

"All bees are declining, not just honeybees," she said. "it is a mystery."

Colony collapse disorder happens quickly. one day, the bees are fine; the next day, they’re gone. not just dead in the hive, but gone, she said.

Some studies point to pesticides as a fatal factor, while others have found an increase in bee parasites. Whether the parasites cause the deaths or just take advantage of bees weakened by something else is still unknown. one study found organic bees on organic farms to be less prone to colony collapse disorder, Horth said.

Whatever the cause, the disappearance of bees worries farmers around the world.

"Do we need to be concerned about what our crops look like?" Horth asked.

She brought her conservation biology class to the zoo to help find out.

The students arranged their soda bottles of cut and glued flowers in a semicircle around the hives and sat down to wait.

"Bee on!" Horth called out after a few minutes. "Do you know which plant the bee landed on? What we’re interested in is what do they see? What do they first land on?"

"That was the all-UV flower," a student answered.

For several hours the students watched the susans. the bees came more often to the flowers with extra-large ultraviolet centers. Duly noted.

"these students are doing cutting-edge science," Horth said. Abbott traveled with Horth to Colorado over the summer to study the size of ultraviolet targets in wild black-eyed susans, and whether growing in sun or shade makes a difference in the size of those targets or bees’ preferences.

Ultimately, the research will be written up and submitted to a scientific journal, preferably either Science or Nature.

"It’s a dream come true," Horth said. "Field science and publication."

At the end of two hours, a final experiment began. the professor took a photo of all the students with all the flowers in all the soda bottles, and she’ll submit that for publication, too – on a Jones soda carton.

Jones soda co. solicits pictures of its product in unusual settings, such as with penguins, and Horth thought she and her students stood a good chance, with all the soda she’d swallowed in the name of science.

"this is better than any cover shot I’ve seen," she said, peering through the viewfinder. "Except maybe the penguins."

Diane Tennant, (757) 446-2478, diane.tennant@pilotonline.com

Researchers have sights set on bees' feeding habits

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