When it comes to sensing danger， termites use their heads and legs. The insects can tell which direction to run using a precise biological timer， scientists report in a new study.

A common African termite builds mounds that stand a meter or more tall. Known as Macrotermes natalensis， these insects also inhabit underground tunnels that stretch over an area as big as a large home. And when a predator comes knocking - like a termite-eating aardvark - the insects sound a natural alarm system.

To sound a warning， soldier termites smack their heads against the floors of their tunnels. This head banging sends vibrations down the tunnels at about 130 meters per second. As other termites pick up the signal， they'll bang their heads， too， relaying the warning. In the wild， this would signal worker termites to go deep into the nest for protection as soldiers head for the source， to do battle.

In the new study， scientists figured out how those soldiers use those signals to know which direction to run. Termites sense the warning vibrations with all six of their legs. They sense it first in the leg nearest the source of the drumbeat. They feel it last in the leg farthest from the source. There's a split-second time delay between those two moments. The Scientists wanted to know how short that delay could be and still correctly send a termite to do battle.

After repeated experiments， the scientists found that the delay from one leg to another had to last only 0.20 millisecond to get a termite pointing in the correct direction. This suggested that the delay was comparable to what a termite in the wild would feel from a vibration in the tunnel.