Wednesday, April 22, 2020

A Honey Bee Swarm, and a Specialist Native Bee on Spring Beauty

A couple interesting sightings of bees in Herrontown Woods recently. Working on trails on April 12, I paused and heard what sound like a buzzing coming from somewhere nearby. With so many machines of transport shut down due to the pandemic, it was quiet enough in the woods to hear what turned out to be a swarm of honey bees 40 feet up in a snag, still erect but completely stripped of branches. They were flying around a hole in the trunk. I went to get another load of stepping stones from our stockpile, but by the time I returned a half hour later, they were gone.

Some internet research led me to an entomologist at Cornell University, Scott McArt, who was kind enough to reply:
"From what you describe, it’s very likely a colony that swarmed. During swarming, half of the bees will leave the hive with their old queen, while the other half of the bees will stay in the hive with a new queen. The exiting bees will typically leave the hive and congregate on a nearby branch for a few minutes or hours, then move on to the next branch (or their new home, once they’ve found it). It’s an impressive sight when thousands of bees assemble onto the branches and/or move en masse to the next location, hence why it’s called a “swarm”." 
"Mid-April is a bit early for swarming, but not unheard of, especially since there’s been some warm weather and flowers popping up over the past few weeks. Aside from a bear getting into the hive, it’s really the only reason you’d see thousands of bees up in a tree right now. So if you didn’t see a bear, I’d say you saw a swarm :)"

Another bee sighting was much more subtle. Over the past month, the most numerous spring ephemeral wildflower has been the spring beauty. Again working on a trail, I happened one day to look down and see a tiny bee visiting one. I was crouching down to catch a photo when the bee dropped off the flower and stood motionless among the dead leaves--reminiscent of the freezing behavior rabbits use when approached. The same happened another day when I again sought a photo.

I was able to find mention of a Spring Beauty Bee (a miner bee named Andrena erigeniae) in a list of specalist bees.

An article in the Baltimore Sun entitled "Searching the Forest for the Bees" describes the bee's lifestyle, which includes only a brief appearance in the spring. It's useful to know that honey bees are not native to America.
"Unlike honey bees, which congregate in hives, most of the forest bees are loners that spend the bulk of their lives in the ground. They emerge for just a few weeks in early spring to pollinate flowering plants, shrubs and trees before the forest leafs out and shades the understory from the sun.

Many are "specialists," Droege said, focusing on a particular type of plant or flower.

For example, he said, there's a bee that specializes in collecting nectar and pollen from spring beauty, a ground-hugging pink or white wildflower that's one of the earliest harbingers of spring. One can't exist without the other, he said. In fact, many flowers have features that attract particular pollinators, while discouraging or excluding others.

"Flowers were all designed by bees," Droege said, over millennia of co-evolution."
 As a botanist, I had naturally assumed that all bees were designed by plants.

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