Spiders Use Fireflies as Glowing Traps

My kids love running around on summer nights, catching fireflies (also called lightning bugs) in jars. But they aren’t the only ones—there’s someone else who likes fireflies, but it doesn’t let them go after it catches them!

Sheetweb spiders are small arachnids who build, as you might guess from their name, webs that resemble sheets, close to the ground.1 One species (Psechrus clavis) lives in the subtropical forests of East Asia, quietly sitting throughout the night, waiting for prey to stumble into its web. Once a moth, beetle, or fly is stuck, the spider crawls over and enjoys its dinner . . . unless that captured bug happens to be its favorite: the winter firefly (Diaphanes lampyroides).

Winter fireflies use bioluminescence (light produced by chemicals) to attract mates. Unlike the fireflies you’re probably familiar with, that blink on and off, this particular species has a steady light. If a firefly gets caught in a web, the light doesn’t go out. It just keeps shining, attracting fireflies and other insects that also get trapped.

Researchers in Taiwan studying these spiders created an experiment to see if leaving the fireflies uneaten helps attract more food for the spider. The scientists placed small lights resembling fireflies in the sheetweb spider webs. They then counted the captured bugs in the webs with lights and compared them to those without lights. And the result? Webs with lights had three times more bugs—and, if you only looked at fireflies, they had 10 times more fireflies!2

It seems the spiders leave their hapless prey glowing for up to an hour after they catch it because it increases their hunting success. Waiting to eat works out great for the spider . . . not so much for the fireflies!

Spiders aren’t animals we often think of as “smart,” but here we have an example of spiders being pretty clever! Whether this is a learned behavior or something God designed them with for a fallen world (that’s called an instinct), we don’t know yet. But either way, it’s pretty cool!

It’s also a reminder that we live in a fallen world. In God’s original creation, everything was created vegetarian (and there are even vegetarian spiders today), but when Adam and Eve sinned, everything changed, and creation went from “very good” to broken. Now, animals either eat other animals or try not to be eaten.

Someday Jesus will come again and make a new heavens and a new earth where there will no longer be any brokenness, and everything will be “very good” once again. Everyone who has put their faith in Jesus, the Light of the world, will live with him forever.

Footnotes

1. Daniel Marlos and Piyushi Dhir, “Sheetweb Spider: All you Need to Know in a Friendly Guide,” WhatsThatBug.com, accessed September 23, 2025, https://www.whatsthatbug.com/sheetweb-spider-all-you-need-to-know/.
2. British Ecological Society, “Spiders Turn Fireflies into Glowing Traps,” Science Daily, August 28, 2025, https://www.sciencedaily.com/releases/2025/08/250828002357.htm.