Have you seen this pollen?
While I was in Exeter, UK for the International Society for Behavioral Ecology (ISBE), I got a message from my two interns: the bees looked sick. In five of our eight observation hives, some of the worker bees had white dots stuck to their back. Even one of the queens had it!
The only thing I could relate the white dots to was ich, a common fish disease. When I was a kid, I had two pet goldfish, Goldie (a typical orange goldfish), and Willie (a black and white goldfish named for Free Willy). One day, my friend decided he was going to help out by feeding my fish. He dumped almost the entire container of fish food into the tank. Both fish got ich, and died a few weeks later. Remembering how quickly ich took my fish, I hoped that this was not a honey bee version of the disease.
The downfall of animal behavior and ecology: you need living, behaving animals to do your research!
Naturally, I googled "jewel weed." I learned that jewel weed is a plant whose anthers (where the pollen is located) are positioned in a way that leaves a white stripe on a visiting bee’s back. (Ironically, crushed jewel weed can also be used as a natural remedy for bee stings.)
But our bees didn’t have a stripe on their back, they had white dots. Since I was at a conference, surrounded by ecologists, I asked someone. Michael Smith, a Ph.D. Candidate in Tom Seeley’s lab, told me that it sounded like pollinia. Michael described pollinia as extra-sticky pollen that gets stuck to places that bees just can’t reach to clean off. Thankfully, it sounded like our bees were not sick.
But this still left me wondering. This is my fourth year keeping observation hives at Tufts, why hadn’t I seen this before? Then the ecologist in me remembered: the northeastern U.S. was (and some parts still are) in a drought. Were the drought conditions forcing my bees to visit flowers they wouldn’t normally visit?
It wasn’t long before I found an anecdotal answer: probably. Near my driveway, there is a small garden with a large cat mint plant and a small flowering tree. After returning from the field one day, I noticed that the flowering tree was covered in bees—honey bees, bumble bees, solitary bees—and the cat mint was not. This was strange.
The cat mint is normally covered in bees (bees love plants from the mint family), and the flowering tree is never covered in bees. Looking at the dried up, unfortunate-looking cat mint, I could tell why the bees were going for the nearby tree instead.
I took out my camera and as I focused on the pollinators, I noticed that the bees were crawling into the flowers, and under the anthers, to get at the nectar. And little white dots—pollinia—were sticking to the bees. I had found the culprit! (Or one of them anyway.)
Moral of the story: white dots on your bees’ backs doesn’t necessarily mean they’re sick and once again, nature is unpredictable. One of the reasons I love being an ecologist!