How fireflies send their love signals

A photograph that gathers the night

The opening image in OddityDrop’s carousel comes from the National Park Service’s Agate Fossil Beds National Monument collection. Its caption identifies a long-exposure night photograph of fireflies over the Niobrara River wetlands, with green traces above the grasses and star streaks in the sky.[3]

That photographic context matters. A long exposure gathers light over a period of time; it should not be read as a frozen view of every insect glowing together. The NPS record does not identify the firefly species in this image, so the picture alone cannot establish which flash pattern the insects were using.[3]

A rhythm with a purpose

Fireflies are beetles, and many produce light through bioluminescence. In their abdominal light organs, a chemical reaction involving luciferin, luciferase and oxygen generates light with very little heat.[1]

The timing is part of the message. NPS describes species-specific patterns that help fireflies find and recognize one another.[4] Among flashing species, males commonly signal in flight and females answer from below.[1]

The familiar big dipper firefly, Photinus pyralis, makes a sustained yellow flash as the male rises, often tracing a J-shaped path. Photinus macdermotti uses paired flashes. The synchronous firefly, Photinus carolinus, produces a sequence of flashes followed by darkness, with nearby insects coordinating their starts and stops.[4] These examples describe different species, rather than one universal firefly routine.

The firefly that skips the flash

Lucidota atra, also called the black firefly or woodland lucy, offers a different version of courtship. Firefly Atlas describes it as a day-active species found in forests and shady habitats across eastern North America.[2]

Its adults do not flash. They use pheromones to attract mates and are often most active from late morning into early afternoon. Their long, flattened antennae are among the features used to identify them; adults may retain small, nonfunctioning light organs.[2]

The distinction is useful when looking at a close-up photograph. A firefly does not have to be glowing, or even be active after dark, to belong to the family.[2]

Leave room for the conversation

For people watching flashing species, darkness is part of the experience. NPS warns that flashlights can disrupt the display and recommends dim red-filtered light only when needed for walking, pointed toward the ground and switched off at the viewing spot.[1]

The park also asks visitors to stay on designated trails and leave the insects uncaught.[1] The spectacle is easier to appreciate when the signals can reach their intended audience.