A
firefly by any other name would shine as brightly. They are sometimes
called lightning bugs or glowworms. But fireflies aren’t flies
at all. They are beetles.
When an insect (or any living organism) is described scientifically,
it’s given a scientific name composed of two parts, genus and
species. The names use Greek or Latin roots and usually describe aspects
or features of the organism.
Members of the firefly genus have had some clearly admiring descriptive
species names given to them, like Lamprocera, which means brilliant
and wax-colored, Microphotus and Macrolampis, big and little light,
Pyrogaster which is fire stomach and, the perennial favorite, Pyropyga,
which means fire rump or fire butt.
All known firefly larvae have photic organs and produce light. The
behavioral function of the light has received considerable speculation
with several theories proposed. The most generally accepted idea is
that firefly larvae use luminescence as a warning signal, communicating
to potential predators that they taste bad. Their glow indicates the
presence of defensive chemicals in their bodies. Glowworm larvae increase
the intensity and frequency of their glow when disturbed, giving merit
to the theory.
Not all firefly species are bioluminescent as adults, but when they
are, one or both sexes use a species-specific flash pattern to attract
a member of the opposite sex. Not as specific as Morse code, perhaps,
but the bioluminescent signals can be a continuous glow, discrete
single flashes, or "flash-trains" with multi-pulsed flashes.
In most species of North American fireflies, during a certain time
of night, males fly about flashing their species-specific flash pattern,
often near ponds, streams, marshes or even depressions or ditches
that retain moisture longer then surrounding areas. Females of the
same species tend to be perched on vegetation, usually near the ground.
If a flashing male catches a female's fancy, she’ll respond
at a fixed time delay after his last flash. A short flash dialogue
follows as he locates her position and descends to meet - and mate.
Non-lighting fireflies are left to locate mates the old fashioned
way - through pheromones, church groups or introductions by friends.
Female fireflies have been shown to prefer certain characteristics
of a male's photic signal, such as increased flash rate, and respond
preferentially to males that possess the signal components that, to
bugs, are quite sexy.
Too much light interferes with the firefly’s luminous signals,
making it harder for fireflies of many species to locate mates. Also,
many firefly species are active only during a certain period of the
evening. They determine what time of night they will flash by the
intensity of ambient light, so there aren’t many fireflies flashing
on clear nights when the moon is full.
There are several theories, none involving a switch, on how fireflies
control the "on" and "off" of their photic organs.
It’s thought to be a chemical reaction, but the exact mechanism
hasn’t been worked out.
The "Oxygen Control Theory" proposes that fireflies turn
their light on and off controlling the oxygen supply to the photic
organ for use in the chemical reaction.
The "Neural Activation Theory" hypothesizes that fireflies
have neural control of structures that release a messenger molecule
in the photic organ, initiating activation of the chemical reaction.
No matter how they turn themselves on and off, the production of light
is very efficient, with very little heat being given off as wasted
energy.
Thank goodness. Lightning bugs that got as hot as light bulbs would
be an unwelcome addition to the party. It might be uncomfortable for
the bug, too.
Although isolated sightings of luminous fireflies have occasionally
been reported from the western U.S., fireflies that glow aren’t
usually found west of Kansas. No one knows why- it’s another
unsolved mystery of lightning bugs, like why they got a photic organ
while people have to rely on cell phones. PL
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