It is amazing to sit out on the porch on these hot summer nights and witness the amazing display of fireflies. The firefly is the official state insect (along with the ladybug).
We are lucky to have such a wonderful insect to watch. Fireflies that glow are typically not found west of the Rocky Mountains. The reason for this phenomenon is not known.
Here in the South and around Chattanooga, fireflies mean summer has arrived. Fireflies are actually beetles, which many people also call lightning bugs.
A blinking courtship
Fireflies use their blinking nature primarily for finding a mate. Fireflies have an adult life of only two weeks. During that time, most of their energy is devoted to courtship. At the very most, males have only about 10 opportunities to mate.
Male fireflies broadcast their availability with carefully timed flashes. Fireflies have detailed flash codes that help to identify the hundreds of firefly species. The flash codes help males attract potential mates of their own species. Fireflies produce green, yellow or orange light in different flight patterns depending on the particular species.
Females, sitting stationary nearby, twinkle back if they are attracted. Research has shown that female fireflies are strongly attracted to males who give longer blinks. They can supply more of the essential prenatal nutrition for their offspring.
How they glow
Tufts University scientists have recently figured out how fireflies blink.
Light cells are located in the last one or two segments of the abdomen of a firefly. It was discovered that flashes start off when the firefly's nervous system sends a signal to the abdominal area. The light is turned on or off by controlling the air supply to these luminescent organs. By regulating the flow of oxygen entering through air tubes on the abdomen, the beetles control the signal.
There is a unique chemical called luciferin in these cells. Luciferin is rapidly converted to light in the presence of oxygen and a specific enzyme. This chemical reaction is known as bioluminescence. No electricity is involved.
The light is referred to as "cold light" because most of the energy used in this process is actually converted to light. Only about 4 percent is lost in the form of heat. In comparison, an incandescent light bulb loses 90 percent of electrical energy to heat.
Shedding light on cancer
Scientists at the University of Texas Southwestern Medical Center recently used the firefly gene in breast cancer research. They were able to put the gene in tumors. Implanted in mice, the tumors emitted light. By tracking how much light is emitted, scientists might better track the size of the tumor.
The procedure should help scientists to be more efficient in their experiments. If they can make cancer cells sensitive to light, then maybe laser light can be used to eliminate them. Various drugs also could be applied. If the cells no longer glow, it means that the drug may have destroyed the cancer.
Turn out the lights
I have noticed that there are more fireflies out just before sunset. Fewer fireflies come out when the moon is full. When the city lights come on, fewer fireflies blink. If possible, reduce any unnecessary yard lighting, which may interfere with the firefly signal. Use motion sensors to turn on lights only when needed.
Tall grass or thick shrubs will provide adult fireflies a place to rest during the day and remain cool. Keeping the lawn mowed high is best for the lawn and the fireflies.
Fireflies are beneficial to the garden. They don't bite. They don't carry disease, and they are not poisonous to people. They are predators on slugs, snails and the larvae of a number of destructive insect pests of crops.
Fireflies are truly one of the great wonders of nature, making our summer evenings more exciting. It is incredible what a simple pulse of light can do.
Contact Tom Stebbins at tstebbins@utk.edu or 855-6113.
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