Bee space is a passageway 1/4- to 3/8-inches wide (6-10 mm) that bees use for moving throughout the hive. In 1851 the Reverend L. L. Langstroth realized that spaces narrower than this were treated like cracks and filled with propolis. Spaces wider than this were treated like construction zones–bees donned their hardhats and filled the areas with burr comb.
Bees–being a little neurotic–like to have their passageways just large enough to fit through: no more, no less. And they never build tunnels through their comb. Every bee, following the unwritten rule, walks around the edges of comb to get to the other side.
Langstroth made good use of this information when he designed his now-famous hive. In order to make the frames moveable, he designed all the areas above, below, and around the combs to fall within the tolerance of bee space. He knew that if he could prevent the combs from being cemented to the hive–or to each other–the frames could be removed, inspected, and replaced.
Many other successful hives have been developed over the years, but they all rely on the concept of bee space to make them work. And as any beekeeper knows, you violate this rule at your own peril. Leave out a frame–or a top bar–for a week and you will have a mess on your hands.
Almost any time you find burr comb, brace comb, cross comb, or propolis seals mucking up the interior of a hive, it is due to a violation of bee space. One of the most common sources of error occurs when equipment purchased from different manufacturers is mixed. Although the pieces seem to fit, in truth, there is often enough difference to give the bees an opportunity for creative engineering.