10/23/2026
Before the leaf blower comes out this weekend: the fireflies of next June are in that leaf litter right now, larvae in year one or two of a two-year wait, and leaves bagged to the curb are fireflies bagged to the curb. Rake the lawn if you must, but rake it onto the beds and under the shrubs, leave the strip along the back fence alone, and skip the grub treatment, since the soil insecticide that kills lawn grubs kills the firefly larvae that are eating your slugs. Then, on a damp night this month, walk the edge of the yard with the porch light off and look down: the larvae glow too, a faint steady green in the litter, and that's the whole crop for 2027, two inches from the rake.
The common firefly east of the Rockies is Photinus pyralis, the Big Dipper, the one that draws a yellow-green J in the air at dusk. It spends one or two years as a larva in soil and leaf litter, a flat, armored thing like a tiny alligator, hunting snails, slugs and earthworms it paralyzes with a bite. It pupates for a few weeks in late spring, and the adult that climbs a grass blade in June gets about three weeks. Most Photinus adults don't eat at all; the three weeks are the search. The male flashes his J about every six seconds, a female in the grass answers two seconds later, and each species keeps its own code, which is how several share one meadow without confusion. The exception is Photuris, the big firefly that comes out later in the night: its females copy the Photinus female's answer, and when the male lands they eat him, as much for his defensive chemicals as his meat.
The lights are the June problem. Studies at Tufts and in Virginia show courtship flashing drops under artificial light and mating drops with it; a female under a floodlight flashes less, and a male has little chance of picking her two-second answer out of the glare of a porch light. What works: outdoor lights off from dusk to about 11 in June and July, motion sensors in place of dusk-to-dawn fixtures, and warm amber bulbs shielded downward for whatever has to stay on. West of the Rockies most fireflies don't flash at all, which is why Californians drive to the Smokies, where the synchronous Photinus carolinus fills the woods at Elkmont in late May and the park runs a lottery for the parking passes; Congaree in South Carolina has its own show in May.
A 2021 assessment put about one in seven assessed US firefly species at risk, and in 2024 the Bethany Beach firefly of the Delaware coast became the first proposed for the endangered list. Habitat loss, lights and pesticides are the three causes, and the fix for all three starts with the rake.
Two years underground for three weeks of light; the leaves you leave this fall are the nights it gets 🌙
