There are certain things that say summer. For many of us, summer means the beach, barbecues, ice cream stands, and family camping trips. If, like me, you are a student of phenology (the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life) there is one nightly event that brings back childhood summer evenings.

My brother and I would get exuberant when the first yellowish-green glowing pulses started along the edge of our yard. My immediate act was to find an empty glass mayonnaise jar and use a screw driver to make holes in the lid. Next, the hunt was on for our lightning bugs. My younger brother was full of energy and ran after each burst of light. I was more patient and waited in the general area for the next signal, moving closer each time. When my jar was full, my brother ended his zig-zag running pattern and we would watch the jar until moving onto the next adventure.

Most people probably know lightning bugs better as fireflies. Both names are misleading as they are neither bugs or fireflies, but beetles in the family Lampyridae. More than 2,000 species have been described worldwide with many species living in the tropical regions. About 40 species occur in New England. Glow-worms are also beetles lacking wings. These can be either juvenile or adult forms of various species. A common characteristic across these beetles is the phenomenon of bioluminescence, the “glow.”

Bioluminescence is a process of producing light by chemical reaction. In fireflies the glow is produced in the abdomen in a special light organ called the photophore. Inside the organ two chemical compounds interact releasing energy in the form of light photons. This process is basically 100 efficient producing almost no heat with light formation. In contrast a standard incandescent light bulb is only 10 percent efficient, losing 90 percent of its energy as heat. Other organisms have a similar process of bioluminescence, such as certain plankton, jelly fish, bacteria, squid, and additional beetle families.

Normally the glow of a firefly is considered part of the ritual to attract a mate. However, some fireflies can use the pulsing light to attract prey or act as a defense mechanism. Female fireflies can lay up to 500 eggs. The larvae are voracious predators feeding on slugs, snails, earthworms, and grubs. In New England the larvae overwinter twice, after the second winter transforming into adults. Adult fireflies only live for a few weeks.

All is not rosy in the world of fireflies. Many species are seeing dramatic declines generally attributed to some combination of light pollution, climate change, pesticide use and loss of habitat. Fortunately, Maine’s fireflies are not listed as endangered or vulnerable at this time. The Mid-Atlantic and Southeastern states cannot make this claim with at least 11 species at risk.

Scarborough Land Trust will host a special field program on fireflies later this month. If you want to learn more and watch fireflies in action, visit https://scarboroughlandtrust.org/event/firefly-walk/. The program is June 22 at 8:30 p.m. and preregistration is required. The program instructor is Scarborough resident, Don Salvatore, a longtime science educator at the Museum of Science in Boston and past curator of the Firefly Watch Citizen Science Project.

For some individuals, understanding the biochemical reactions taking place in a firefly might take away the mystery. To me, this just adds to the incredible complexity and diversity of life. Take a few minutes to slow down this summer and enjoy one of nature’s light shows.

Andrew Mackie is executive director of the Scarborough Land Trust. He can be reached at amackie@scarboroughlandtrust.org.

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