Science Puzzle
Why Do Bees Build Hexagons?
Honeybees store honey and raise their young in wax cells, and they build every cell as a six-sided hexagon. Thousands of them fit together into a honeycomb with no gaps at all.
Triangles and squares also fit together with no gaps. Round cells would hold larvae neatly. Why do bees build hexagons?
The Answer
Hexagons give the most storage space for the least wax.
Wax is expensive for bees. They make it from glands on their bodies, and it takes several kilograms of honey to produce one kilogram of wax. So the best comb is the one that holds the most honey with the shortest total length of wall.
Circles waste space: they leave gaps between them, and the gaps still need walls around them. Only three regular shapes fit together with no gaps at all: triangles, squares and hexagons. Of those three, the hexagon is the closest to a circle and encloses the most area for a given length of wall. Neighbouring cells share their walls, too, so no wax is doubled up.
Pappus of Alexandria, a Greek mathematician, admired this around 1,700 years ago. Mathematicians long suspected that hexagons were the best possible way to divide a flat surface into equal cells using the least total wall, out of every shape imaginable, curved or straight. Nobody could prove it until Thomas Hales did in 1999. It's known as the honeycomb conjecture.
Scientists still argue about exactly how the bees do it. One idea is that they build roughly round cells and the warm, soft wax is pulled into straight walls where neighbouring cells meet, just as bubbles in a foam press into flat-sided shapes. Others think the bees shape each wall themselves.
The principle: Efficient packing. Of the regular shapes that fit together with no gaps, hexagons enclose the most space for the least wall, so a honeycomb stores the most honey for the least wax.