Stinging surveyors

by David Sugarman

Most of us are familiar with the wonderful architecture of bee and hornet nests, with their perfectly symmetrical hexagons. How do these insects create such evenly aligned structures, time and time again?

The cells that hold the eggs and developing young of the hornet Vespa orientalis are symmetrical in both their architecture and orientation.

Scientists in the Netherlands and Israel have found the key to this perfect alignment may be a tiny magnetic crystal found in each cell. These crystals form a network that may act like a level, helping the hornets judge the symmetry of the cells and the direction of gravity as they build.

Using their saliva, the hornets glue a crystal of the magnetic mineral ilmenite to the centre of the roof of each cell as they begin building. The cells with their hanging crystals move in response to gravity as the adult and larval hornets jostle the nest. The crystals, about a tenth of a millimetre in diameter, are composed mainly of titanium, iron and oxygen.

Where do the hornets get these crystals?

They may collect them from the environment near the nest, but they may make the crystals themselves—hornet bodies contain titanium and iron.

Another example of nature's tool kit in action.