Washington ? This is that strange, sweet part of summer when life stops for a beetle’s behind.

On a June night, a woman blast-e-mailed her Bethesda, Md., neighborhood: “Go outside RIGHT NOW. Look into the dark.” At a park in Arlington, Va., a man clicked one flash from a penlight and waited for an insect to signal back.

This is firefly season, the best and brightest in several years. Scientists say a wet spring has made the Northeast, a lightning-bug-friendly region, even more so, and hordes of the insects are now spending the last days of their lives floating over lawns and blinking in treetops.

In the daytime, most fireflies — there are about 2,000 species of them worldwide, 200 in the United States — look like a second cousin to the junebug. But at night, chemical reactions produce a glowstick light from their abdomens, each tiny bug worth about 1/40th of a candle.

This spectacle holds even more magic if you know what they’re saying.

“Then the whole world of fireflies opens up to you,” said Sara Lewis, a professor who studies the family Lampyridae (“shining ones”) at Tufts University outside Boston. There is seduction and rejection, codes and code-breaking, mating and eating alive. “You can watch the dialogue,” she said.

Across the country, scientists worry that firefly numbers have been driven down by lawn pesticides and sprawling concrete. Also, chemical companies have paid a per-bug bounty to get the chemicals in their tails, which are used in scientific research.

“We were a little worried,” said Michael Raupp, a professor of entomology at the University of Maryland, “but they seem to be back in force.”

In recent decades, scientists have been able to translate snippets of the firefly babel. They say the flashes are a muddle of conversations, usually several species communicating in the same meadow.

They’re talking — as animals usually are — about sex.

The bugs in the air are all male, each flashing out a pattern distinctive to his species. The Big Dipper firefly, one of the most common in Washington, gives a long flash while flying in a “J” pattern. Photinus macdermotti flies straight and slow, flashing twice every six seconds. Some are Morse-code dots — blink.blink.blink — and some are dashes, bliiiink … bliiink.

Their audience is down in the grass, females who wait an interval, specific to their species, before responding with a blink or two.

“This tells the male, ‘There’s a female here, and let’s go down and investigate further and maybe mate,’ ” said Jonathan Copeland, a biology professor at Georgia Southern University.

Maybe. The life of a male firefly is not easy.

In some cases, the come-hither responses are a deadly ruse, from a larger species that has cracked its prey’s code. When the male flies down to investigate, this femme fatale firefly will eat it, extracting chemicals it needs to ward off the things that might eat it.

In other cases, the males have trouble finding their mates in the forest of grass blades. Or the females don’t flash back at all. Recent research has shown they sometimes prefer males who flash longer and faster — which, for reasons involving the mechanics of firefly sex, may be better mates.

They’re all working with a time limit. Fireflies spend years as larvae underground and then emerge to fly only for a week or two. Their only mission is to reproduce before they die, and more than half of males will fail.

“Some males are better than other males,” Copeland said, and they advertise that prowess through their flashes.

Humans who’ve outgrown the fireflies-in-a-jar phase (just fine for the fireflies, scientists say, as long as the jar contains a damp paper towel and the fireflies are released at the end of the night) can bluff their way into this dialogue. Alonso Abugattas, of the Arlington County parks department, said he waits for a male to flash and then responds with a quick flash from a penlight.

“You can convince the firefly that there’s a female there, so he’ll get closer, and he’ll do it again,” Abugattas said.