Insect of the Week: Five Myths About Fireflies

silent sparksMyth #1. Fireflies are flies, and lightningbugs are bugs

Truth: They have two different nicknames, but both refer to the same group of insects. Throughout much of the southern United States they’re called lightning bugs, while in the north and east they’re more often known as fireflies. Yet these insects are neither flies nor bugs – they’re actually beetles! What makes them beetles? Their hard wing covers that fold down to protect the delicate flight wings when the insect is resting.

Myth #2. If you’ve seen one firefly, you’ve seen them all

Truth: The firefly family, known as Lampyridae, includes more than 2000 described species worldwide. Here in North America, we have more than 200 different firefly species. These include the lightningbug fireflies, which use quick, bright flashes to find mates. These are mainly found east of the Mississippi River. But more common in the western U.S. are the glow-worm fireflies, which have glowing, wingless females, as well as dark fireflies, whose adults don’t light up at all.

Myth #3. Fireflies only light up for sex

Truth: In every species within the firefly family, the larval stage is capable of producing light. Because larvae are too young to reproduce, their bioluminescence appears to serve as an anti-predator warning. Fireflies contain chemicals that are toxic to many vertebrate predators. For these nocturnal larvae, bioluminescence is similar to the bright coloration used by monarch butterflies: it shouts out “I’m toxic – stay away!”

 Myth #4. Fireflies mean summertime

Truth: The spectacular summer lightshows produced by adult lightningbugs are just the tip of the firefly life cycle. Adult fireflies fly for merely a few weeks, but can spend nearly two years living underground during their larval stage. Juvenile fireflies spend months feasting on earthworms, snails, and other soft-bodied creatures. Ferocious carnivores, firefly larvae inject victims with paralyzing neurotoxins, then secrete digestive enzymes to liquify and ingest their prey.

Myth #5. There are so many fireflies, they don’t need protection

Truth: Certain firefly species, like the Big Dipper firefly Photinus pyralis, are abundant and occur in many habitats across a wide geographic range. But others are restricted to small, isolated populations or are habitat specialists, and these are in greater need of protection. Worldwide, many firefly populations are under threat from habitat loss, light pollution, and altered rainfall patterns due to climate disruption. In addition, firefly ecotourism is gaining popularity, and increasing numbers of visitors can impact both adult and larval habitats. Within the past century, fireflies in the U.S., Japan, and China have also been commercially harvested from wild populations.


Sara Lewis, who has been captivated by fireflies for nearly three decades, is a professor in the Department of Biology at Tufts University. Her work has been featured in numerous publications, including the New York Times, Scientific American, and USA Today. Lewis lives with her husband in Watertown, Massachusetts.

Silent Sparks
The Wondrous World of Fireflies

For centuries, the beauty of fireflies has evoked wonder and delight. Yet for most of us, fireflies remain shrouded in mystery: How do fireflies make their light? What are they saying with their flashing? And what do fireflies look for in a mate? In Silent Sparks, noted biologist and firefly expert Sara Lewis dives into the fascinating world of fireflies and reveals the most up-to-date discoveries about these beloved insects. From the meadows of New England and the hills of the Great Smoky Mountains, to the rivers of Japan and mangrove forests of Malaysia, this beautifully illustrated and accessible book uncovers the remarkable, dramatic stories of birth, courtship, romance, sex, deceit, poison, and death among fireflies.

The nearly two thousand species of fireflies worldwide have evolved in different ways—and while most mate through the aerial language of blinking lights, not all do. Lewis introduces us to fireflies that don’t light up at all, relying on wind-borne perfumes to find mates, and we encounter glow-worm fireflies, whose plump, wingless females never fly. We go behind the scenes to meet inquisitive scientists who have dedicated their lives to understanding fireflies, and we learn about various modern threats including light pollution and habitat destruction. In the last section of the book, Lewis provides a field guide for North American fireflies, enabling us to identify them in our own backyards and neighborhoods. This concise, handy guide includes distinguishing features, habits, and range maps for the most commonly encountered fireflies, as well as a gear list.

A passionate exploration of one of the world’s most charismatic and admired insects, Silent Sparks will inspire us to reconnect with the natural world.


This post is part of a series, explore additional posts here<< Insect of the Week: A Guide to Lightningbug LinguisticsInsect of the Week: the False chinch bug >>