LINCOLN, Mass. — Sara Lewis is fluent in firefly. On this night she walks through a farm field in eastern Massachusetts, watching the first fireflies of the evening rise into the air and begin to blink on and off. Dr. Lewis, an evolutionary ecologist at Tufts University, points out six species in this meadow, each with its own pattern of flashes.

MATING In many fireflies, pairs stay coupled for hours while the male, lower, gives the female a protein package injected with sperm, called a nuptial gift.

Along one edge of the meadow are Photinus greeni, with double pulses separated by three seconds of darkness. Near a stream are Photinus ignitus, with a five-second delay between single pulses. And near a forest are Pyractomena angulata, which make Dr. Lewis’s favorite flash pattern. “It’s like a flickering orange rain,” she said.

“Most people don’t realize there’s this call and response going on,” Dr. Lewis said. “But it’s very, very easy to talk to fireflies.”