ResearchBlogging.orgA lot of discussion occurs about “light pollution” at night, but some recent research suggests there’s another issue–polarized light pollution during the day.

Smooth, dark buildings, vehicles and even roads can be mistaken by insects and other creatures for water, according to a Michigan State University researcher, creating “ecological traps” that jeopardize animal populations and fragile ecosystems.
It’s the polarized light reflected from asphalt roads, windows – even plastic sheets and oil spills – that to some species mimics the surface of the water they use to breed and feed. The resulting confusion could drastically disrupt mating and feeding routines and lead insects and animals into contact with vehicles and other dangers, Bruce Robertson said.

This isn’t a new issue–there is a long history of papers documenting the attraction of cars to aquatic insects laying eggs.  A 2006 paper specifically looked at different colors of cars–apparently red vehicles attract other things besides police cars.

You just can’t help but be depressed reading some of the papers–this one covers how glass buildings act as a “polarized light trap” and lure hapless caddisflies to their doom.

Are we so far down the road of shiny plastic and glass objects that we can never come back? Unfortunately, I have to conclude that we are.  What this will mean for insect populations, we can only speculate.

But I’m betting it won’t be good.

Link to the actual papers:

Horváth, G., Kriska, G., Malik, P., & Robertson, B. (2009). Polarized light pollution: a new kind of ecological photopollution Frontiers in Ecology and the Environment DOI: 10.1890/080129

Kriska, G., Csabai, Z., Boda, P., Malik, P., & Horváth, G. (2006). Why do red and dark-coloured cars lure aquatic insects? The attraction of water insects to car paintwork explained by reflection–polarization signals Proceedings of the Royal Society B: Biological Sciences, 273 (1594), 1667-1671 DOI: 10.1098/rspb.2006.3500

Kriska, G., Malik, P., Szivák, I., & Horváth, G. (2008). Glass buildings on river banks as “polarized light traps” for mass-swarming polarotactic caddis flies Naturwissenschaften, 95 (5), 461-467 DOI: 10.1007/s00114-008-0345-4

G Kriska, G Horvath, & S Andrikovics (1998). Why do mayflies lay their eggs en masse on dry asphalt roads? Water-imitating polarized light reflected from asphalt attracts Ephemeroptera. Journal of Experimental Biology

Posted by Gwen Pearson

Writer. Nerd. Insect Evangelist. Have you heard the good news? BUGS!


  1. I wonder if there’s something we can do to help the buggies distinguish between man-made polarisation and the natural type. Then again, I suppose even if there were it’d be a pretty hard sell to spend money coating buildings in stuff to save caddis flies.

    And then there’s the matter of undesirable aquatic bugs like mosquitos. Maybe there’s some way to trick them into laying their eggs in a fake lake to bake in the sun rather than growing up to make new generation of bitey blighters.

  2. This could explain why I have found dead giant water bugs in a mall parking lot.


  4. Is there any way to, say, paint the building a lighter color so the insects won’t mistake them for water?

    Asphalt could be replaced with concrete (as is the case with a lot of roads where I live), but I’m not really sure what could be done to make glass emit less polarized light.

  5. I’ve heard of the above articles before, or at least some similar study in reference to metallic cars and dragonflies.

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