A multiple-exposure image captures the flight of fireflies at the Taguchigawa River in Japan. (ASAHI SHIMBUN VIA GETTY IMAGES)

Silent Sparks

Sara Lewis

You think fireflies are delightful, right? Sure you do. Magical, beautiful aeronauts, slow-moving enough for children to catch, stingless, and they don’t carry diseases. Enchanting.

Well, think again. Or at least think about baby fireflies, of the species Lampyris noctiluca, because they’re about as enchanting as Hannibal Lecter. In “Silent Sparks: The Wondrous World of Fireflies,” Sara Lewis paints an unappetizing portrait of Lampyris’s larval stage — which lasts for most of its life — when it is a cruel and voracious predator. Hatching about three weeks after the egg is laid, the teeny-tiny newborn sniffs out its prey, a juicy snail several times its size. With sharp, sickle-shaped jaws, it punctures a hole in the snail’s skin, tenaciously clings to its shell and eats it alive, a sucking process that takes three days. Over the next 18 months or so, this Lampyris will devour about 70 snails, increase its body weight by 300 times and shed its skin repeatedly. After a brief stage as a pupa, it will emerge as either a male firefly or a female glowworm, fat, wingless and several times as big as the male. Both adults stop eating and focus full time on sex. The mating process . . . well, it’s pretty unappetizing too, so never mind. In any case, like almost all fireflies, they’ll both be dead in a few weeks.

Lewis, who has spent years and traveled the word studying fireflies, tells this and other fairly icky tales with glee — but to be fair, she spends even more of this intense, almost obsessive book describing the radiantly appealing aspects of the firefly world.

One of the most awe-inspiring is the synchronized flashing of Photinus carolinus fireflies, a spectacle that attracts tens of thousands of visitors annually to the June “Light Show”in the Great Smoky Mountains. “It wasn’t until the forest was completely dark that we saw the first flash,” she writes of her own experience. “A few moments later a dozen male fireflies took flight around us, broadcasting their typical mating call: six rapid bursts of light followed by six seconds of total darkness. Suddenly the forest came alive with flying sparks, and thousands of male fireflies were flashing together in lock-step synchrony! . . . All the scientific descriptions that I’d read had left me totally unprepared for the transcendental thrill of this rhythmic, pulsating display.”

And that doesn’t hold a candle, as it were, to the Pteroptyx fireflies in Thailand, where along a 500-foot stretch of river, 35-foot-tall trees are covered in fireflies, hundreds of thousands all flashing in rhythm in a display that goes on every night for months.

There’s more — including a chapter on how Japan, with a long tradition of loving and capturing fireflies, brought them back from near extinction in part via commercial breeding houses. And how Tokyo, where no fireflies survive, stages an annual festival with the aid of 100,000 solar-powered, glowing table-tennis balls taking the place of the living creatures. It’s all pretty amazing.

— Nancy Szokan