BACKYARD NATURALIST: Summertime, Kids and Fireflies
By Nanci Bross-Fregonara
There's something about watching children chase fireflies on a warm summer evening that makes you feel all's right with the world. Is it their excitement that forces us to refocus on the little things or is it that the arrival of fireflies means the beginning of summer's warmth and renewal? Whatever the starting point, the mental journey always seems to take us back to our own pickle jars with holes poked in the lids.
The firefly, lightning bug or glowworm, is actually not a fly at all, but rather a beetle; one that has long been revered, despite its small size. The Aztecs, for example, used the metaphor of fireflies as meaning “a spark of knowledge in a world of ignorance or darkness,” according to William F. Lyon of the Ohio State University Extension Service, “and the Chinese thought these twinkling little creatures came from burning grass.”
Today, we know differently. The flashing light emitted by their tail is actually caused by bioluminescence, a chemical reaction caused when oxygen and two rare chemicals, luciferase and luciferin, combine. When the chemical adenosine triphosphate (ATP), which is found in every living cell, is added to this formula, it will light up. This mixture is found even in firefly larvae and is responsible for the beetle's “glow worm” nickname.
This light is very unique, Lyon explains. For example, in an electric lightbulb, 90 percent of the energy expended is heat and only 10 percent is light. In a firefly, nearly 100 percent of the energy is given off as light. This has mystified researchers and inspired a method of detecting energy problems in human cells, such as those affected by heart disease, muscular dystrophy and cancer. Special electronic detectors, using firefly chemicals, have even been placed in spacecraft to look for earth-like life forms in outer space, he explains. “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 a signal is recorded by scientists on earth.”
For fireflies however, this amazing capacity for creating light serves one major purpose: finding a mate. The male firefly emits different signals, depending on the species, in order to attract a female. With a ratio of 50 males to one female, there is a lot of blinking going on! A female will respond with either one flash or two, depending on the species, and within a few minutes the two will meet up and mate. Interestingly, female fireflies of one species have the capacity to mimic the mating signals of other species. Once she has successfully lured the other male in, she will eat him!
“Even when a firefly is under stress, such as being caught in a spider's web, its taillight glows brightly,” Lyon explains. “The shock of a firecracker or thunder may cause a field of fireflies to flash in unison.”
Unfortunately those fields of fireflies are becoming increasingly threatened. If you think you are seeing less of these magical creatures than when you were younger, chances are you are right. The use of lawn chemicals and excessive use of lights has adversely affected fireflies. They need a high level of darkness in order to see the signals clearly.
To attract more fireflies, cut down or eliminate the use of lawn chemicals, reduce the amount of outside artificial light, and provide low-hanging trees and areas of tall grass for them to rest on. Then sit back, wait until the sky darkens and listen for the youthful shouts of excitement. Just like capturing winter's first snowflake or that first dive into fall leaves, it is a seasonal moment to savor.
Nanci Bross-Fregonara is a public information specialist stationed in Elkins.