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Why
do fireflies light up?
The Chinese thought these twinkling little creatures came from burning
grass. A European
legend warned that if a lightning bug flew in the window, someone
was going to die.
Aztecs used the term firefly metaphorically, meaning a spark of
knowledge in a world
of ignorance or darkness. American Indians collected lightning bugs
and smeared
them as decorations on their faces and chest.
The
firefly is much more efficient than man in producing a "cold
light", containing no ultra
violet rays, with a pale yellowish or reddish green in color and
a light efficiency of 96%.
The ordinary incandescent light has an efficiency of roughly 10%,
most of the energy
being wasted as heat. The light-producing organ is located in the
sixth, or the sixth
and seventh abdominal segments.
The
taillight contains two rare chemicals, luciferin and luciferase.
Luciferin, a heat resistant
substrate, is the source of light; luciferase, an enzyme, is the
trigger; and oxygen is the fuel.
A
body chemical, ATP (adenosine triphosphate), converts to energy
and causes the
luciferin-luciferase mixture to light up. Small internal injections
of ATP in the firefly tail
cause flashes of light that can be measured quantitatively. If you
will notice, the firefly
turns on its light when flying upward, at intervals of about 5.8
seconds. In the dark
periods it coasts downward again. You may also have noticed that
hundreds of
them synchronize their flashes to appear simultaneously.
As
all living cells contain ATP in a rather constant concentration,
injection of the
firefly's chemicals quickly detects energy problems in human cells
(different reaction
between normal and cancerous cells). The firefly technique is used
to study heart
disease, muscular dystrophy, urology, antibiotic testing, waste
water treatment, and
environmental protection. Luciferin and luciferase are used in research
on cancer,
multiple sclerosis, cystic fibrosis and heart disease.
The
ability of these insects to produce cold light (bioluminescence)
has led to new flashlights
and flares on the market today. Special electronic detectors, using
firefly chemicals,
have been placed in spacecraft to look for earth-life forms in outer
space. When as little
as one quadrillionth of a gram of ATP enters the rocket's detector,
a flash of cold
light is given off and the signal is recorded by scientists on earth.
Other detectors
warn that milk, food or water may be bacteria contaminated.
.From
... Ohio State University
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