PARIS (AFP) Jul 29, 2004 A quirky beetle which lays its eggs in smoulderingtrees may one day help fight the forest fires that each year ravage parts of theMediterranean coastline, southern California and Indonesia.
That’s the hope of a pair of German zoologists who are devoted fans of theEuropean jewel beetle (Melanophila acuminata), an opportunistic species which isreputedly able to detect a forest fire from 80 kilometers (50 miles) away.
Even while the forested area is still smoking after a blaze, these beetlesarrive in droves to take part in a mating frenzy.
The females crawl up the sides of the scorched trees and lay their eggs inthe blackened bark. The eggs hatch into larvae, which then munch on the wood asthey grow.
“Ask any forest firefighter and he will tell you that the jewel beetlealways gets there before him,” Helmut Schmitz, of the University of Bonn’sZoology Institute, told AFP in a phone interview.
“The creatures have fantastic heat sensors. That’s what gives them theircompetitive edge over other species and enables them to survive.”
Jewel beetles are well known in many countries, thanks to the pretty metalliccolours, in yellow, blue, red and orange, that swirl across the top of theirtough, one-centimetre (0.4-inch) long shell.
But the beetle’s beauty is more than skin deep.
Its underside has so-called pit organs, located where its legs are attachedto the body.
Within each pit are scores of sensors that are highly receptive to infraredradiation which help it to detect heat spots from many kilometers (miles) away.
The sensor comprises a sphere made of cuticula, the same substance that formsthe insect’s armour. The sphere is connected by nerve strands to a sensory cell.
The cuticula is particularly responsive to thermal radiation with awavelength of about three micrometers, typically the same given out by a bigforest fire.
As it absorbs this heat, the cuticula sphere expands. That minute movement isdetected by the sensory cell, which in turn triggers bug’s nervous system, thusdirecting the insect towards the chance of mating party.
Schmitz and a doctoral student, Martin Mueller, have now replicated thebasics of the beetle’s sensor, using simple manmade materials.
The cuticula sphere has been replaced by a small plate made out ofpolyethylene — the same plastic used in supermarket shopping bags — whichabsorbs infrared in the three-micrometer range and also expands in response,triggering a piezo crystal, which gives an electrical discharge when it isdisturbed.
The sensor has been tested on sources of heat at close range, and Schmitzbelieves it could detect a small fire at a range of perhaps 100 metres (yards).
“It is only a prototype, to prove that the principle works,”Schmitz said.
“We hope to come into contact with companies to improve it, to make itmore sensitive especially.”
Their dream is that, in a refined form and manufactured in commercialquantities, their gadget will become an inexpensive guardian of forests that arevulnerable to blazes caused by lightning or pyromaniacs.
Scattered in vulnerable areas and linked to satellite positioning, thesensors would issue a radio alarm if they detected a fire outbreak.
Commercial infrared sensors of this kind already exist and, compared to theprototype, “are better by a factor of 100,” Schmitz said.
However, to achieve this sensitivity, these gadgets have to be cooled byliquid nitrogen to below zero degrees Celsius (32 degrees Fahrenheit), whichmakes them far too complex and cumbersome, as well as prohibitively expensive,to serve as forest watchdogs.
Jewel beetles are not the only animal species with infrared capabilities.Scientists are also taking a close look at the mosquito and two kinds of snake,the pit viper and giant constrictor.
Part of this interest is military, because cheap, sensitive and miniaturisedinfrared sensors would be useful for missiles, perimeter security, range findersand sniper scopes.