Insect of the Week: Synchronous Symphonies

Among all the glamorous mating rituals that have been shaped by evolution, the displays performed by certain synchronously flashing fireflies might rank as the most spectacular. For reasons we don’t yet understand, only a few lightningbugs show a remarkable behavior: thousands of male fireflies will match up their rhythms to flash together in unison. Two distinct types of synchronous flash behavior have been observed: one type involves stationary males, while the other takes place among roving (flying) fireflies.

In southeast Asia, certain Pteroptyxmale fireflies sit in communal display trees along tidal rivers, where each night they spend hours flashing together in perfect synchrony. Females fly to these stationary aggregations, known as leks, where mating occurs.

Writing in the journal Science in 1935, Hugh Smith, a naturalist living in Thailand, described these dazzling displays:

Photo credit: Radim Schreiber

Imagine a tree thirty-five to forty feet high thickly covered with small ovate leaves, apparently with a firefly on every leaf and all the fireflies flashing in perfect unison at the rate of about three times in two seconds, the tree being in complete darkness between the flashes. Imagine a dozen such trees standing close together along the river’s edge with synchronously flashing fireflies on every leaf. Imagine a tenth of a mile of riverfront with an unbroken line of Sonneratia[mangrove] trees with fireflies on every leaf flashing in synchronism, the insects on the trees at the ends of the line acting in perfect unison with those between.


Because fireflies congregrate so predictably in the same trees, night after night for months, native boatmen once navigated among the twisting waterways using firefly display trees as landmarks.

But stationary flash synchrony doesn’t happen in any North American fireflies. Instead, several of our lightningbug species show a kind of wave synchrony, where flashes are synchronized locally among males flying within line-of-sight of each other. In the southern Appalachians, the synchronous symphony of Photinus carolinusattracts thousands of visitors to admire these flying males as they coordinate their six-pulsed courtship flashes with those of nearby males. These fireflies create waves of synchronous flashing that moves through the forest in the Allegheny National Forest and Great Smoky Mountains National Park. Similar displays of wave synchrony among roving males can be seen in mating displays of Photuris frontalis in Congaree National Park, South Carolina, Photinus knulli in Arizona, and Macrolampis palaciosi in Tlaxcala, Mexico. When they’re in a dense population, males of other fireflies will sometimes synchronize their flashes for a short time.

Wherever you find them, synchronous fireflies make an indelible impression – they are certainly one of Earth’s great natural treasures!


Learn more about firefly synchrony in Silent Sparks: The Wondrous World of Fireflies, and on the author’s firefly blog.

silent sparksSilent 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.