Science at home: What killed the bees?

by Treloar Bower, Curator of Education

I’ve been contemplating dead bees. One day last week, I noticed many dead bees: one group was on the sidewalk to the north of the Museum, the other group was on the driveway at my parents’ house in Windsor. In each place, the number of dead bees was between 5 and 7. Is it possible that there is always that many dead bees lying around and I just haven’t ever noticed? Somehow I doubt it. So I got a bee in my bonnet (pun intended, sorry – couldn’t resist) to find out why these two groups died because it seemed too much to be coincidence.

First, I mentioned the dead bees to Katie, who is our resident entomologist, for all intents and purposes. She told me that bees will clean out their hives every now and then, pushing the bodies of dead bees out of the hive. Did two hives have a “fall cleaning”? I considered that, but if hive cleaning was the origin of these two different groups of dead bees (which would be a heck of a coincidence), I’d expect to see the bodies in one location, closer together, under or near a hive, right? Instead, these dead bees were lying over distances of about 10 feet, seemingly too scattered to be tossed from a hive, not to mention, I couldn’t spot a hive near either one of these locations.

Next on my idea list: are these dead bees related to Colony Collapse Disorder (CCD)? First, my disclaimer: I’ve read a little bit on CCD, but I have no depth of knowledge about it. I do know that adult worker bees disappear from a colony suffering CCD (the cause of which is currently being investigated, but no definitive answer has been identified yet). Since those adult worker bees aren’t dying at the hive, they are dying elsewhere. Could two groups of adult bees, perhaps abandoning their hives as part of CCD, and separated by about 10 miles, each die with the individuals within five to ten feet of one another, all within a day? Again, it’s a coincidence I find hard to accept.

So then I thought about wildfire smoke. On Tuesday, September 1, the same day I saw the dead bees, of the Colorado Department of Public Health and Environment issued a smoke advisory for north-central Colorado, recommending that people limit their outdoor activity. Smoke from the large wildfires in southern California as well as numerous smaller ones in other locations, including here in Colorado, blanketed our community that day, making the sky very hazy and reducing the quality of our air to “moderate.” I wondered, could wildfire smoke kill bees? I thought it unlikely, but I logged onto the Internet to find out.

Online, I found numerous sites about beekeepers’ use of smokers on hives. Smoke prevents bees in a hive from recognizing the alarm pheromones released by guard bees when the hive is opened by a beekeeper. Smoke also causes a feeding response: where there is smoke, there is fire, so bees feed in case they must abandon their hive due to approaching wildfire. Along with this information, however, I learned that smoke, in fact, does not kill bees.

In a fun side note, I found an online newsletter from the Puget Sound Bee Association with an article written by a beekeeper describing the day a wildfire approached his hives, which were behind a blockade set up by the fire department (Smoke and Honey, by Jason Nelson, on page 3). A firefighter let him access his hives with the promise not to use a smoker – he could light no fire of any kind. The beekeeper reported that this wasn’t a problem: there was enough ambient smoke in the air that his bees were calm. And he didn’t mention any dead bees.

So I’m left still wondering, what killed all of those bees, in two places, in one day? If you have an idea, please share!

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1 Response to “Science at home: What killed the bees?”


  1. 1 pelagian7 September 23, 2009 at 8:17 am

    I have a garden of perenials that are native to the area. My home is drowning in several species of bees. I love it. I have not been stung in years even though I weed and water next to them.

    One guess for Bee deaths: the hybrid annuals so popular in suburbia are sickening them. I notice that when the bees are feeding on the pollen of those ferals, they are more hostile and hyper.

    I realize this is unscientific and even if my observations are true, several other possibilities could account for the behavior.

    Yet, the placidity of the bees in the native perenials is impressive. And since I went away from hybrids my bee population has jumped exponentially. Honey bees to bumble bees and they all seem healthy.
    Brian, in Mn. U.S.

    Did the dead bees have their stingers intact? They may be chemically influenced to attack or made sick or just more agressive.


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