Fireflies signal through the short summer nights
June 25, 2026
The light is still fading at nine o'clock. In the understory along Bethesda's wooded edges, where flowering dogwood and pawpaw hold the middle layer and the canopy closes overhead, the first flashes appear low to the ground, maybe a foot or two above the grass. They are yellow-green, brief, and arcing slightly upward. By the time full dark settles in, there are dozens of them.These are common eastern fireflies, and what you are watching is a conversation. The males fly and flash; the females wait, perched on vegetation, watching. The male's signal follows a precise pattern: a single flash lasting about half a second, then a pause of roughly six seconds, then another flash. The arc of the flight is part of it too. Females who are ready to mate flash back after a fixed delay, typically about two seconds. That timing is the key. Males scanning the dark learn to read it. A female who answers at the right interval draws the male toward her, and he flashes again, and she answers again, and he homes in. The whole exchange can take several minutes before the male lands.This is peak season for them. The nights are the shortest they will be all year, which means the window for signaling is compressed. But the warmth matters as much as the darkness. Common eastern fireflies are most active when air temperatures stay above roughly 21 degrees Celsius after sunset, and summer nights here hold that heat. The flashing typically begins in the first hour after dark and tapers off by midnight. On a warm, still night with low wind, the signals carry well and the activity is dense. On cooler nights, or nights with rain, it falls away quickly.The light itself is produced in the abdomen, in a specialized organ that runs a chemical reaction involving a compound called luciferin, an enzyme called luciferase, and oxygen. The reaction produces light with almost no heat, which is unusual for a light-producing process. The firefly controls the flash by controlling the oxygen supply to the organ. The precision of the timing, the duration, the interval, is all physiological, controlled by the nervous system. Different firefly species in the same habitat use different flash patterns and different colors, which is how a female tells her own species from others flying nearby. In the same meadow edge, you might have several species active at once, each running a different signal.The larvae spend most of their lives underground or in leaf litter, where they are predators of soft-bodied invertebrates including earthworms and snails. The adult firefly, the one flashing now, does not eat at all, or eats very little. The adult stage is entirely about reproduction. The females of some firefly species mimic the flash responses of other species to lure males and eat them, but common eastern fireflies do not do this. The adults live only a few weeks.Spotted lanternfly, an invasive species now established in this area, feeds heavily on a wide range of woody plants in summer, and its presence has altered some of the understory structure that fireflies depend on. Invasive Amur honeysuckle thickens the shrub layer in ways that can reduce the open, grassy edges where males fly and females perch to watch. These are slow pressures, not sudden ones, but they shape what the habitat looks like over time.If you are outside now, or near a window facing a wooded edge, look low. The males rarely fly more than a few meters off the ground during the early display. The flash lasts less than a second, then the beetle coasts dark for six seconds before flashing again. If you count the interval, you can tell whether what you are seeing is a male searching or a female answering. The females tend to flash from a fixed point; the males move. Watch one long enough and you can see the arc of the flight between flashes, a faint shape moving through the dark.
Yellow-crowned night herons hunt crayfish at dusk
June 24, 2026
Along the marshy edges near the Tidal Basin, the light holds long into the evening now. The days are at their longest, and in the hour before dark, yellow-crowned night herons move into the shallows. They are stocky, short-necked birds for a heron, built lower to the water than a great blue heron, and they move through the marsh with a patience that reads as deliberate. They are hunting.The yellow-crowned night heron is a specialist in a way that most herons are not. While great blue herons take fish, frogs, and whatever else crosses their path, yellow-crowned night herons have organized much of their foraging life around crustaceans. Crayfish, in particular. Their bills are heavy and stout compared to other herons, reinforced enough to handle armored prey. Their eyes are adapted for low-light conditions, which is why they are out now, in the last hour of daylight and into dusk, when crayfish are most active in the shallows. A foraging bird will stand motionless for a stretch, then lunge, pinning a crayfish against the mud or lifting it free of the water entirely. Larger crayfish get battered against a hard surface before the bird swallows them. The heron flips them to go down headfirst, avoiding the claws.Right now, this behavior is not just feeding. It is provisioning. Nests in the mid-Atlantic are active through early summer, and adults are moving between foraging sites and nest trees, carrying food back to nestlings. Yellow-crowned night herons tend to nest in wooded areas near water, often in small colonies, and the adults work the surrounding wetlands in shifts. The crayfish they pull from these shallows are calorie-dense and relatively easy to subdue compared to a fish that can twist free. For growing nestlings, that reliability matters. The marsh is not decorative here. It is functional infrastructure for the breeding effort happening in the trees nearby. If you are near the water's edge, look low along the bank. A yellow-crowned night heron standing still can be easy to miss; the gray and black patterning on the adult's head blends against shadow, and the bird does not flush easily.Crayfish are not passive in this equation. They are nocturnal by preference, sheltering under rocks and debris during the day and moving into open shallows to feed after dark. The heron's crepuscular timing is not coincidence; it corresponds with the window when crayfish are most exposed. Several species of crayfish occupy the freshwater and brackish margins around the Washington area, and in summer their populations are large. Juveniles hatched earlier in the season are now active in the shallows, and these smaller individuals are well within the heron's range. The water temperature here is running warm, which keeps crayfish metabolism high and active, and keeps the herons well-supplied.The great blue heron is present along this same shoreline, taller and more visible, and it will take a crayfish when one presents itself. But the yellow-crowned night heron does not compete with it directly. The two species are working different prey, different depths, different hours. The yellow-crowned is lower, slower, more deliberate in its search. It probes under overhanging banks. It waits near submerged root masses where crayfish shelter. The foraging style fits the prey.The sun is down or nearly so where you are standing. The swifts that were cutting arcs overhead have pulled back. In the quiet that follows, listen for the yellow-crowned night heron's call, a short, sharp bark, higher-pitched than the great blue heron's, sometimes given when a bird lifts off the water and crosses to another section of marsh. It is not a frequent sound, but this is the hour when you are most likely to hear it. The water in the shallows barely moves.
