Streetlights Draw Insects at Ground Level

Click here to listen to this podcast

You've probably seen clouds of insects swirling round a streetlamp at night. But something you may not have noticed is that streetlights attract bugs to the ground below them, too—especially carnivorous bugs, like beetles. So says a study in the journal Biology Letters by researchers at the University of Exeter. Thomas W. Davies, Jonathan Bennie and Kevin J. Gaston,"Street lighting changes the composition of invertebrate communities"]

The researchers set up 28 traps in the grass below and between streetlamps in the English town of Helston, in Cornwall. They collected captured insects at dawn and dusk over three days, and ended up with nearly 1,200 specimens. Turns out, more bugs hung out under the lights than between them. And that was true at night and day—suggesting that streetlights permanently upped the value of the buggy real estate below them.

The researchers also found greater numbers of predators and scavengers under the lamps—like ground beetles, harvestmen and ants—because it may be easier to hunt for prey with the help of a spotlight.

With artificial lighting increasing globally at 6 percent a year, the authors say there's a chance light pollution could shake up food webs in unforeseen ways. Call it a bug in the system.

—Christopher Intagliata

[The above text is a transcript of this podcast.] 

Follow Scientific American on Twitter @SciAm and @SciamBlogs. Visit for the latest in science, health and technology news.
© 2012 All rights reserved.