Serendipity Nature's smoke detectors

THROUGHOUT history, humans have learnt lessons from animals and plants, copying mother nature's designs and stealing her secrets. The idea for turning wood pulp into paper, for instance, came from insects.

Until the 18th century, books were expensive because paper was made from linen rags, which were in short supply. Even the bodies of the dead would be wrapped in wool rather than linen so that any spare fabric could be sent to the paper industry. However, in 1719, the French naturalist Rene-Antoine Reaumur noticed that some wasps build paper nests from wood: "The American wasps form very fine paper by extracting the fibres of common wood of the countries where they live. They teach us that paper can be made from the fibres of plants without the use of rags and linen, and seem to invite us to try to make fine and good paper from the use of certain woods."

More recently, nature has taught us a lesson through the apparently suicidal behaviour of a particular type of insect. Most creatures flee from forest fires, but fire-fighters have observed that so-called fire beetles actually fly towards the danger. The swarms can be so intense that they sometimes hamper fire-fighting efforts. Biologists wondered why these beetles exhibited such lemming-like behaviour, and concluded that they were risking death to be the first to lay their eggs on smouldering trees.

Healthy trees exude toxic chemicals which kill larvae, but a dying tree in a burnt forest is not so poisonous, thus providing an ideal laying site and giving the fire beetle an advantage over the rest of the insect world. Interestingly, only 65 per cent of eggs laid in a burnt tree hatch the same year. Twenty five per cent hatch the following year, and 10 per cent the year after that. The beetles need forest fires to breed, and yet there is no guarantee of a forest fire every year. Hence, the delayed hatching acts as an insurance policy against fire-free years.

Earlier this year, in the journal Nature, Dr Stefan Schutz at the Justus Liebig University, Germany, described how the fire beetle might lead to better smoke detectors. The fire beetle is able to sense smoke at a distance of several miles, mainly because its antennae are covered in hairs that contain proteins capable of reacting with the phenolic compounds found in wood smoke. The problem with current household smoke detectors is that they can be confused by smoke-like chemicals, such as car fumes, thereby giving false alarms. However, the fire beetle antennae seem to be foolproof. Dr Schutz's colleagues have already built a bio-sensor that consists of beetle antennae incorporated within a block of electronics. The next stage is to find a way building replica antennae, which would avoid having to use real ones.