How much do honeycomb cells tilt?
After reviewing the list of biology books in my last post, Mike Riter of New York had a good question about the angle of honeycomb cells.
Do any of those books tell us how much of a tilt, in degrees, the honey bees build their cells so honey won’t leak out as they cap them? I can’t find this anywhere. Seems 40-50 years ago every honey bee article I read had the answer. So what happened? Did we go from everybody knowing to nobody knowing? Did they use to think they were all at the same angle and now think they build them with some degrees of difference?
I mentioned this measurement several years ago in a post called, “Why honey doesn’t run out of the comb.” The reason for slanting cells is obvious. Nectar is about as thick as water and would easily flow out of a horizontal cell. Even brood food and larvae could slide out and drop through the hive with a splat if the cells weren’t properly tipped.
Is there a standard angle?
In my previous post, I used the numbers I found in The Beekeeper’s Handbook. On page 19 the authors write: “The cells of the honeycomb do not lie on a completely horizontal plane: the openings are slanted slightly upward by 9–13°. This prevents stored materials and brood from spilling or rolling out of the cells before they are capped with wax.”
But since Mike asked the question, I widened my search. In The Biology of the Honey Bee (p. 81), Mark Winston says, “Unlike most other social insects, honey bees build their cells horizontally rather than hanging vertically, although they are angled up at about 13° from base to opening to prevent honey from running out.”
In Honey Bee Biology and Beekeeping, Caron and Connor mention the phenomenon but don’t quantify it (p. 78): “Bees build the beeswax combs progressively downward, sloping the cell walls slightly upward.”
The final book where I found a reference was The ABC & XYZ of Bee Culture. A diagram on page 177 shows the upward tilt from both sides of the comb midline. The caption reads as follows: “Diagram showing the slight angle (~17°) upward the opening a typical cell has from the midrib.” As far as I can see, there is no further mention in the text.
Leaving the books, I went online. Wikipedia says, “The cells slope slightly upwards, between 9 and 14°, towards the open ends.” That sounds like The Beekeeper’s Handbook, although they don’t reference it.
Causes for variation
Altogether, these sources give quite a bit of latitude: 9 to 17 degrees. I suspect that the variation may be due to differences in genetics as much as anything. My husband suggested that the angle might be influenced by the tip of the entire hive, especially when foundation is used. If the foundation in not vertical, the bees would have to build a really sloped cell (at least on one side) to keep the nectar from running out. This is purely conjecture, of course, but it makes sense in a practical sort of way.
Brushing your bees
And speaking of practicality, whenever I’m writing about angled cells I like to remind beekeepers how to brush bees from a frame. If you brush bees downward while the cells are angled upward, the bees’ legs can easily get caught on the cell rims and be ripped off or damaged. Knowledgeable beekeepers brush bees from a frame by flicking the brush up, not down. Not only are the bees less likely to be injured, but they’re easier to get off the frames.
Honey Bee Suite