Spring Treetop Flasher (Pyractomena borealis) - The Brutal Life of Firefly Larvae

The larvae of the Spring Treetop Flasher (Pyractomena borealis). Watauga Bluffs State Natural Area.

Lightning bugs (a.k.a. fireflies) are incredible. If you haven’t experienced the sheer wonder inspired by thousands of these harmless, lovesick, and bioluminescent insects lifting into the summer night, it’s an experience worth adding to your bucket list. But fireflies have a dark history; each is born as a stone-cold killer. One of the best examples of this seemingly oxymoronic behavior is the larval Spring Treetop Flasher (Pyractomena cf. borealis) who hunts beneath the frozen leaf litter of winter.

Armored larvae have retractable heads with sharp, scissor-like mandibles, and often wander around “headless” to protect their fragile mouthparts. Snails, slugs, and other beetle larvae are the usual victims of an infant firefly. Adults are large, colorful beetles (bigger than most other firefly species), and take courtship flights during the cold, barren evenings of early spring. Males use rapid, green flashes in budding canopy to get the attention of females, especially over boxelder swamps.

Females respond to individual males with their own sequences of green, bioluminescent “challenges.” Potential mates are tested by the ability to harmonize their own light shows with the interested female’s. Still, the only true lightning bugs you’re likely going to see in Appalachia right now are roaming around underfoot, with each future firefly living a vicious childhood as a bizarre, ruthless predator.