Common eastern
Photinus pyralis
Also called: Big Dipper firefly, common eastern firefly
At a glance
- Flash
- A single warm-yellow flash in a rising J-shaped swoop, about once every 5–6 seconds
- Habitat
- Lawns, meadows, forest edges and gardens, usually near moisture
- Range
- Eastern and central North America
- Season
- Late spring through mid-summer
- Size
- 10–15 mm
- When active
- The first hour after sunset
Overview
The most familiar firefly of North American summers. At dusk the males fly low over open ground, each tracing a J-shaped path and emitting a single warm-yellow flash on the upswing — the movement that earns it the name 'Big Dipper.' Females wait in the grass and answer with a flash of their own a couple of seconds later, and the two exchange signals until the male finds her.
Like all fireflies it is a beetle, not a fly, and it makes its light through a cold-light reaction of luciferin, the enzyme luciferase, and oxygen — almost no heat is wasted. The larvae live for a year or more in damp soil, glowing faintly (the original 'glow-worms') as they hunt snails, slugs and worms. The winged adults live only a few weeks and barely feed; their whole job is to find a mate and signal.
How to identify
Look for the unmistakable J-stroke — the flash brightens as the male sweeps upward — and note the warm yellow colour, not green. Active low over open lawns and meadow edges in early darkness.
Conservation
Still common, but sensitive to lawn pesticides and light pollution. A dark, un-sprayed yard with some longer grass gives local populations exactly what they need.
Sources & further reading
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