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TERMITES under attack from fungi send out an alarm signal warning the rest of
the colony to run away. The insects signal danger by frantically waggling their
heads, sending shock waves through the nest.

Dampwood termites (Zooteropsis angusticollis) nest in rotting logs
and trees, eating the very homes they live in. Because they can鈥檛 digest wood,
friendly bacteria in their guts do this for them. 鈥淭hey also live in a
pathogenically rich environment,鈥� says James Traniello of Boston University. And
because many individuals are packed close together, it鈥檚 easy for diseases to
spread through the colony.

This creates a problem. Unlike ants, which make their own antiseptics,
termites can鈥檛 use chemical weapons against microbes without risk to their
friendly bacteria. So they have devised an early-warning system instead.

Traniello鈥檚 team made this discovery when they created an artificial nest
with a central gallery divided down the middle by a wire mesh. The termites
could escape via small tunnels connected to each side of the chamber. The team
then infected one segment of the nest with the fungus Metarhizium
anisopliae, whose spores can latch onto the termites and kill them by
injecting poisons.

When concentrations of the fungus were low, the termites started grooming
each other to remove the spores. But when more fungus was added, they began
waggling their heads in different directions. 鈥淚t produces a vibration,鈥� says
Traniello. 鈥淚t鈥檚 a seismic signal.鈥�

Other termites sense this signal in their legs. When fungus-ridden
individuals raised the alarm, uninfected ones on the opposite side of the mesh
escaped down the tunnels. 鈥淭he signal conveys the information `remove yourself
from this area鈥�,鈥� says Traniello.

Termites didn鈥檛 try to escape when the researchers placed a foam mat into the
nest, which dampens vibrations, proving that the warning signal wasn鈥檛
chemically transmitted.