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Night
Light
The
Aztecs saw them as rep-resenting a spark of knowledge in a
world of ignorance. Today they are aiding research on cancer,
heart disease and other disabling conditions. They may also
help us detect life in outer space. They hang out in my garden
and, as the dusk’s light dims, they provide a short-lived
aerial show, stretching hyphens of greenish-yellow light along
lumbering flights amid raised vegetable beds and thickening
summer vegetation.
Fireflies are pretty amazing creatures. I’ve been fascinated
with these bugs since I first saw their blinking lights hovering
through the summer air. Why and how do they do this magic?
Why do they only seem to flash about for only a short time
just as darkness is setting in, and where are they all the
rest of the day?
Following one flashing wonder through my garden, I focused
my vision where I thought the insect would next flash. I was
generally off a bit in my prediction, always looking for straight
lines where such things seldom exist. The bug seemed to not
take any evasive measures from my pursuit. It seemed intent
on other concerns, flashing at a steady rate.
Fireflies (aka lightning bugs) are actually nocturnal beetles
of the Lampyridae insect family. Their adult lives
are short, sometimes flashing for as long as a week if they’re
lucky. They tend to prefer warm and humid weather, with the
greatest diversity of species being found in tropical areas
of Asia, Central America and South America. They emerge in
many parts of the eastern United States during the warm summer
months, but for some unknown reason they don’t light up in
the North American lands west of Kansas.
While their days of adulthood are few, most of their life
is lived out in a larval stage that prefers the damp cover
offered by decomposing wood, leaves and plant debris. Many
species of the flashing bug tend to settle in or near sources
of water, preferring ponds, streams and wetlands, though some
species can survive in arid areas. When they’re not doing
their aerial light shows, they’re hiding out in the cool shade
of nearby plant life.
Female fireflies lay their eggs in damp earth. The eggs hatch
after about three weeks into tiny larvae that some have described
as appearing turtlelike in shape. Unlike the seemingly laid-back
adults, these larvae are aggressive predators voraciously
devouring such garden pests as snails, slugs, cutworms and
mites. They have sickle-shaped mandibles through which they
inject their prey with a compound that both anesthetizes and
initiates the digestive process. Firefly larva (aka glowworms)
are distinguished from other small critters by the glowing
spots that can be found on their undersides and can remain
in this larval stage for as long as two years.
In late spring, maturing larvae go into a pupa stage like
butterflies, however instead of a thread cocoon, they take
up residence in a tiny ball of mud. After about 10 days of
entombment, the adult beetle emerges and immediately focuses
its short remaining life on locating a sex partner to help
ensure the next generation of flying flashers. Beneath dark-brown
wing covers the adult firefly hides a yellow-green abdomen.
Females tend to have smaller areas of luminescence than males.
To attract more of these beetles to one’s yard, firefly expert
Marc Branham suggests reducing or eliminating the use of lawn
chemicals, reducing “extra lighting” which creates “photic
noise” for the bugs, and providing vegetation where the bugs
can stay cool during the day.
Research indicates that the flashings of the mature firefly
serve two main functions. First, they are a form of communication
to potential mates. Each species of firefly has its own distinct
set of flashes. Males tend to be the ones we see flashing
around in the air, generally outnumbering females at a ratio
of about 50 to 1. Females often remain in the vegetation below.
If they see a particularly “sexy” flasher above, they will
flash back and engage in a series of photic communications
that may culminate in mating.
The second function of the flashing is to warn possible predators
that they should avoid eating this bug. The flashing frequency
of the beetles is known to increase in stressful circumstances.
Among the substances in the bug’s “tail light” are lucibufagins,
toxins that can be quite poisonous to potential predators.
When two Australian bearded dragon lizards died in the Philadelphia
Zoo not that long ago, autopsies revealed that they died from
eating fireflies. A number of other exotic reptiles and amphibians
not accustomed to these flashers in their natural environments,
have died when they mistakenly snagged fireflies for a meal.
The light given off by these bugs is far more efficient than
anything Thomas Edison could have dreamed up. While incandescent
bulbs waste about 90 percent of the energy they consume in
the form of heat, the simple “cold” light of the firefly converts
almost 100 percent of the energy used into light. The light
is produced through the action of two rare chemicals contained
in the bug’s butt. Luciferin produces the light when it is
acted upon by the enzyme luciferace, which functions as a
chemical trigger. Oxygen is the fuel burned in the reaction
and ATP (adenosine triphosphate) acts as a form of chemical
fuse that causes the mix of luciferin and luciferace to go
critical.
Luciferin and luciferace are important substances in health
research and space exploration. These bioluminescence chemicals
and their reaction to ATP (contained in all living cells)
help in the detection of problems in human cells. They have
furthered research on cancer, heart disease, multiple sclerosis,
cystic fibrosis and antibiotics. These chemicals have also
been used in electronics developed to probe space for extraterrestrial
life and to detect bacterial contamination in food and water
down here on the planet.
It appears that the simple little firefly has done a lot more
for humans than just fascinate us with their flashing.
—Tom
Nattell
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