What’s the deal with fireflies?

Why do they flash?

Romance. Adult fireflies use flash patterns to identify members of same species and opposite sex. Females of two species have been shown to prefer males with higher flash rates and stronger flash intensity, but otherwise not much is known about the flash patterns.

How do they flash?

A chemical reaction in the firefly’s light organ causes bioluminescence when oxygen can reach the photocyte cells. The photocytes are deprived of oxygen by neighboring mitochondria, which consume all the oxygen present, leaving the light cells dark. When a nerve signal instructs cells to produce nitric oxide, the mitochondrial respiration is halted and the oxygen present is free to be used in the bioluminescence reaction.

(Fun fact: I was first introduced to mitochondria as a child in the book A Wind in the Door.)

What else is cool about fireflies?

  • There’s a place in the Smokies where a species called synchronous fireflies flash at the same time. It’s not known why they’re synchronous: it could be competitive — if I flash first, the girls will notice me; or it could be collaborative — if our group flashes together, we have a better chance of getting the girls’ attention. Here’s a video. It’s a little bit creepy. Peak flashing in the park is late May to mid June.
  • Adults fireflies only live about 21 days, and don’t eat.
  • One species has a bluish light.
  • Females flash too but don’t usually fly.

Fireflies and lightning bugs are the same critters. Which do you say? I say both, but probably more often use “lightning bug.”


Scientific American

National Park Service

Tufts Journal


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