Ecology

A sign of summer: fireflies

Lizzy Ryan
Strawberry Hill Nature Preserve

(8/2022) The days are scorching, and the evenings are clear and warm. You are sitting outside in the evening by a campfire enjoying the fresh air. As it becomes darker, you begin to see little spots of blinking, yellow lights illuminating your backyard. They are back: Pennsylvania’s state insect, the firefly or lightning bug. Fireflies are one of the sure signs of summer.

In 1974 Pennsylvania inducted the firefly as the state insect after students in the Upper Darby Elementary School noticed that Pennsylvania was missing a state insect. They soon submitted their proposal to the General Assembly to officially instate the firefly as the "state insect."

Contrary to their name, fireflies are not "flies," but are actually in the beetle order, Coleoptera and in the family Lampyridae. "Beetles have been around for some 297 million years. Beetles also make up around 38% of insect species. Like all beetles, fireflies undergo a complete metamorphosis, with four distinct stages: egg, larva, pupa, adult." (Xerces Society)

There are around 2,000 species of fireflies worldwide. Most species are nocturnal, meaning their activity is more abundant at night. Interestingly enough, not all species of fireflies produce light!

"Fireflies are classified under five main subfamilies." (firefly.org)

The first subfamily is called the Lampyrindae. This subfamily of firefly is found most commonly across North America; they are the kind you will likely see in your backyard, donning the yellow-green light. These fireflies are about half an inch long, and not all species in this subfamily light up.

The second subfamily is Photurinae. They produce a darker green light and are about an inch long. Those found in this subfamily are found in California, Utah, Colorado, Texas, and Mexico. The fireflies in this species tend to be cannibalistic.

The third subspecies, Luciolinae, is found over Europe, Australia, and East Asia. They are the largest subfamily of fireflies.

The fourth subfamily is called Cyphonocerinae. They are found in North America and Eurasia. One species in this subfamily does not light up while the other displays a very weak light.

The last subfamily is called Ototetrine. They are found in North American and Eurasia and do not produce light.

Fireflies live in a vast variety of habitats ranging from forest, meadow, urban, and wetlands. Many species of lightning bugs start their larval lives in rotting wood and underground while others start their lives aquatic or semiaquatic. Depending on the species, fireflies can stay in their larval form for months or even years. Most species have a short lifespan as adults. Adult fireflies make fantastic pollinators as they primarily feed on nectar and pollen. Firefly larvae, on the other hand, are carnivorous and like to feed on snails and worms.

Lightning bugs communicate using their bioluminescence. "Fireflies have dedicated light organs that are located under their abdomens. The insects take in oxygen and, inside special cells, combine it with a substance called luciferin to produce light with almost no heat." (National Geographic) Both males and females will communicate by flashing a specific pattern to attract mates, defend their territory, and warn predators.

Since fireflies use their bioluminescence to attract mates, scientists believe that light pollution is having a negative effect on their ability to find a mate. Artificial light will actually disrupt their light patterns. Scientists have noticed that even a simple passing car’s headlights will disturb their flashing patterns made to attract mates. Too much light pollution disrupting their light patterns can lead to difficulty in finding a mate and, therefore, leads to a decrease in fireflies born the next year. Sadly, for this reason, and many more, populations of lightning bugs are dwindling all over the world. Many researchers attribute this to development, pesticide use, and light pollution. Because many species start their lives underground and in rotting wood, development destroys their habitat. Pesticides are also killing off fireflies during their larval stages when they are underground or underwater.

So, what can you do to help the firefly population?

One thing you can do is turn off any outside lights during the evening. That way, artificial light will not disrupt their light patterns. Another thing you can do is let your leaves lie where they fall; don’t rake them up at the end of the season. Let natural leaf litter and downed logs build up because natural rotting debris is a source of habitat for the little guys in their larval forms. Without the natural litter, there is no place for them to grow up. Fireflies love being around areas of water so having water features in your yard will provide additional habitat for them. Just remember, be careful not to leave stale, standing water around. Make sure the water is moving, otherwise you will attract an uninvited guest: the mosquito!

Limiting lawn chemical use is also important if you wish to help the firefly population thrive. You hear about the dangers of lawn chemicals all the time. Pesticides and fertilizers often applied to lawns can poison the larval and adult forms of the firefly as well as other beneficial insects. Many communities will spray for mosquitos at night when fireflies are lighting up the sky seeking out mates. This can destroy populations of lightning bugs. Communities should use broad spectrum mosquito sprays and avoid spraying at night when fireflies are active. Another thing you can do to help the fireflies is limiting lawn mowing. Many want to keep their lawn perfectly manicured in order to keep up aesthetics. However, fireflies like to live in long grassy areas. Try not to mow your grass as often or keep sections of longer areas for the fireflies to congregate. (firefly.org)

If you’re looking for an interactive way to learn about fireflies, consider looking into Mass Audubon. Mass Audubon is doing a citizen science project called ‘Firefly Watch’. To join this scientific research, all you have to do is spend at least ten minutes once a week during firefly season watching lightning bugs. Participants count the number of flashing fireflies they see over the course of ten minutes in three ten-second periods as well as the number of flashing patterns. Then you submit your observations online. It’s as easy as that! To learn more, visit www.massaudobon.org

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