Lightning bugs are a fascinating summer phenomenon. The flashing green lights on a summer’s night never fails to captivate both young and old alike.

When I was a boy, all the kids would be running around the neighborhood at night with canning jars trying to capture a few lightning bugs, or as some called them — fireflies. The jars with the glowing bugs inside would occupy a special place in our bedrooms so we could watch the bugs as we fell asleep for the next several nights.

Even today, it’s easy for me to sit outside and watch the sparkling green lights of fireflies for hours. But fascination aside, what are lightening bugs and how and why do they glow?

Lightning bugs are officially members of the beetle family and there are over 2,000 different species of firefly in the world. Roughly 180 of these different species live in North America. There are five subfamilies in the firefly family. The most common group is called Photinus and the most common lightning bug is the photinos pyralis, also known as the common eastern firefly.

This firefly’s range is anywhere in the United States east of the Rocky Mountains. When observing the green glow of a lightning bug around Dunn County, it is most likely a photoinus pyralis.

Lightning bugs produce their light by a process known as bio-luminescence. The light emitted is cold light which makes the light very efficient. One hundred percent of the energy used to make the light is emitted as light. Fireflies use two chemicals, luciferase and luciferin, which combine with adenosine triphosphate (ATP) to make light.

Luciferin glows under the proper conditions. It acts as an enzyme that triggers light emission and ATP is a chemical that transports energy within cells. What is still not understood by scientists is how the lightning bugs turn their lights on and off. All other animals that use bio-luminescence glow constantly, while only lightning bugs can flash their lights. Maybe someday science will solve this mystery.

Fireflies flash their lights for a variety of reasons. One reason is that the males are flashing their lights to attract a mate. The males of each species have a specific light sequence that they use to attract a mate. Females of the same species recognize the pattern and respond with their own flashes. The male then hooks up with the female to continue the lightning bug cycle.

Fireflies may also be using the flashes to attract prey. The female of the photinus family of fireflies can mimic the flash patterns of males of other species of fireflies. The unsuspecting male flies to the flashing female expecting a bit of fun and ends up as supper instead. Other species of fireflies use their flashes to attract non-firefly bugs to eat. Fireflies taste terrible and they may be poisonous to some bugs. The flash of light serves as warning to other critters that says “do not eat”.

The larva of fireflies also lights up. They emit a glow and consequently are known as glow worms. One species of firefly that lives in the southern Appalachian Mountains can synchronize its flashes with other fireflies. Hence, all the lights are going off and on at the same time. How the bugs coordinate this feat is another scientific mystery in need of solving. Some species of fireflies do not produce any light even though as larvae they did glow. Even firefly eggs glow.

In addition to eating male fireflies, the different species of firefly eat a wide variety of other insects. Some lightning bugs, and especially their larvae, eat slugs, cutworms, and aphids. Other fireflies eat pollen and nectar from flowers and plants. Some lightning bugs have no mouths and do not eat in this stage of their life.

The firefly we see at night are at the end of their life cycle and usually only live for three to four weeks. After the males and females mate, the female lays her eggs in moist soil. The larva hatch in three weeks and begin to glow and feed upon inebriates like slugs. The larval form of fireflies lasts from one to two years. The larvae then go into a pupa stage that lasts for three weeks and then they emerge as adult fireflies.

Firefly populations are crashing in many locations. No one is sure as to the exact reason for the decline in numbers, but several factors seem to be at work here. Light pollution may be one factor in declining firefly numbers. Without the darkness of the night it is hard for the fireflies to see each others’ flashes and to attract prey. Less food and less mating means fewer fireflies.

Pesticides that are applied to gardens, yards, and fields will also kill lightning bugs. Sprawl destroys firefly habitat. Disturbing the ground kills the larva and eggs and impervious surfaces make it impossible for the remaining fireflies to even lay their eggs. Fireflies are territorial so if their territory is destroyed, they disappear.

The glow mixture chemicals in fireflies is being used in biomedical research for things as diverse as food safety, cancer, diabetes and allergies.

It is time for young kids, adolescents, parents and grandparents who are young at heart, to get out in the night and watch the fireflies. Go ahead and catch one or two and put them in a jar. Keep them in your room and enjoy the glow for no more than two days, then release them back into the outdoors.

Jim Swanson is a Menomonie resident. He can be reached at


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