In 1859, Charles Darwin published The Origin of Species, detailing his theories of evolution. This was the culmination of years of painstaking work studying the characteristics of numerous species of plants and animals. Honey bees were one of the species that fascinated Darwin. He knew that proving that the complex honeycomb structure of their nests had evolved from far simpler designs would be central to his theories of natural selection.
Most bees build simple irregular structures but the architecture of honey bees’ hives is altogether more complex. Their ability to build intricate perfectly hexagonal structures of wax honeycomb in their hives features prominently in his chapter on ‘Instinct’.
Understanding How Honeybee Combs Evolved
Bees have existed since the Tertiary period, but finding good fossil records of the nests of extinct species is difficult. Instead Darwin used three examples of living species to demonstrate how cell building had evolved. The simplest nests are built by bumblebees who build spherical pots in an irregular comb. In the nests of the Mexican stingless bee, Melipona domestica, flat sides are created when two or more spheres interact. Darwin reasoned that it would only take two more evolutionary steps to create honey bees’ hexagons – cells of equal size at an equal distance apart.
But these steps appeared insurmountable to Darwin for some 20 years as he grappled with his thoughts on cell building. Yet again his correspondence with other naturalists helped him focus his ideas. Keeping bees was a common pastime in the Victorian era; Darwin was not alone in finding their home life fascinating.
Help From Fellow Beekeepers
He enlisted the help of beekeepers and naturalists across the country. By building on the work of Francoise Huber, George Waterhouse and William Tegetmeier, Darwin began to understand how the bees worked. Waterhouse in particular was coming to similar conclusions; he suggested that bees first made cylindrical cells and the hexagons formed as the result of lateral pressure, as the cells were built close together. Darwin felt driven to study this process in action.
Studying bees at work is difficult as they need warmth to build the cells. To create heat, the bees crowd around each other, obscuring the view.
Experiments at Down House
One of Darwin’s local beekeeper friends, the vicar John Innes, came to his rescue. He helped Darwin to hive bees himself and together they constructed an observation hive. One such hive can be seen at Down House, Darwin's home in Kent, where he lived for the last 40 years of his life.
Honey bees normally build the cells from scratch but by introducing wax blocks into his observation hive Darwin could study the construction of the cells. Darwin found that by placing thin blocks of wax into a hive containing recently swarmed bees, the bees would form hemispherical bases on the artificial wax.
He extended this work by using a coloured wax and showed that the colour was delicately diffused by the bees in an even fashion throughout the growing structure. Darwin’s ideas that the bees cooperate to construct the hive were taking shape.
His experiments revealed that the instinct of the bees was all about balance. They stand at the same distance from each other all using a sweeping motion to build up equal spheres. By leaving untouched the planes of intersection between these spheres, a hexagonal structure builds up.
The secret of bees' honeycomb construction is still not fully revealed. How do bees actually manipulate the wax to form each cell? Pieces of wax may simply be moved or kneaded into place.
Conservation at Work
Honey bees’ instincts do not only create hexagonal cells that are practical and strong.
Darwin thought that the precise construction of the hexagonal honey comb is likely to confer evolutionary benefit through conservation. Less wax is used than in the construction of triangular or square cells. By sharing common walls, the bees save wax and therefore require less nectar. Maximum amounts of honey can be stored with the minimum amount of wax.
Sources
Williams, J. Darwin’s Bees. The Central Association of Bee-Keepers: Bringing science to the beekeeper. Published by Streamset, UK. ISBN: 978-1-904379-18-8.
Darwin, C. The Origin of Species (1859). Wordsworth Editions Ltd. Published 1998. ISBN: 978-1-85326-780-2.
Catherine Whitlock - After some fun years in medical research poring over a microscope, I now write about the scientific wonders that others have magnified.I ...
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