Sluggin' Along: Ships that pass in the night: Common Eastern Firefly

It's lightning bug season! If you live in the Eastern US, you've probably seen the unmistakable flashes around dusk. Large for a member of this genus, the Common Eastern Firefly (Photinus pyralis) is 10-14 mm long. Its elytra are blackish-brown and finely, densely wrinkled. The side margins and suture of the elytra are yellow. The pronotal disk is pinkish with a black spot, and the pronotum is convex.

It's uncertain whether the adults of this species feed, but the larvae will feed on insect larvae, slugs, and snails. After they hatch, the larvae take about two years to reach maturity. They overwinter twice and then pupate during the final spring.

As a defense against predators, an adult P. pyralis engages in "reflex bleeding" (similar to ladybugs), where it sheds blood intentionally. A predator such as an ant may become entangled in the sticky substance, while birds or spiders will be repulsed by the foul-tasting lucibufagins (steroids) in the blood. Pupae might glow at night as a warning signal to predators.

Flashing is used to find a mate. In male fireflies of this species, the light organ occupies the entire ventral surface of the three most posterior segments. In females, it only covers a portion of the third posterior segment. Inside the organ, the enzyme luciferase uses oxygen, luciferin and ATP to trigger bioluminescence. While males go out on patrol, females will sit and wait for an attractive male to show himself. She responds to his signal after a couple seconds. Also called the Big Dipper Firefly, the male P. pyralis flies in a J-shaped trajectory, lighting as it ascends. The flashing occurs at an earlier time of day than with most fireflies.

Think of it as two ships signalling to each other at night with signal lamps! Henry Wadsworth Longfellow wrote in his famous poem:

Ships that pass in the night, and speak each other in passing, only a signal shown, and a distant voice in the darkness; So on the ocean of life, we pass and speak one another, only a look and a voice, then darkness again and a silence.

I found this male in the late afternoon before sunset.