Nature Bulletin No. 27 August 11, 1945
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation
or lightning-bugs, were unusually late this year. Few were
seen before July 4th and in some localities they are still scarce. The
firefly is a beetle, of the family Lampyridae. The adults are short-lived
and eat little or no food. They are nocturnal in habit, resting on the
leaves cool, damp bushes during the day. The female lays a hundred or
more eggs at the base of a plant in a damp, moist place, generally near a
stream. The larvae hatch and live for one or two years in the soil.
The firefly is much more efficient than man in producing a "cold light",
containing no ultra violet rays, with a wavelength from 0.00051 to
0.00067 millimeters in length, pale yellowish or reddish green in color,
with 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. Here are stored two compounds known as
"luciferin" and "lucifrase". A system of fine air tubes, controlled by the
nervous system, bring most air to the luciferin, oxidizing it and
activating the lucifrase to produce light reflected through thin skeleton
of the abdomen.
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. The females respond about two
seconds later, and the males fly toward them.
That 96% efficiency was made for love.
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Update: June 2012