Light pollution may disrupt firefly sex

BALTIMORE — The glow of LED lights might throw off the flirtations of fireflies, new tests suggest.

Females of the big dipper species (Photinus pyralis) don’t flash back at twinkling males quite as often as expected when forced to court under artificial light, says ecologist Ariel Firebaugh of the University of Virginia in Charlottesville. And these less flashy females didn’t end up mating. (In natural twilight, five out of 28 fireflies did.) Likewise, artificial light in the lab reduced female flash responses to a fake male (a Christmas tree bulb brightening in a male’s rhythm). Yet LED illumination outdoors didn’t seem to curtail males’ flirt-flashing. Light pollution may unsettle the female response, Firebaugh suggested August 11 at the annual meeting of the Ecological Society of America.

There have been few, if any, other experiments testing details of how artificial light at night affects fireflies’ back-and-forth light shows, Firebaugh says. Much remains to be explored, she adds, including whether light pollution will affect the abundance of fireflies. So far, repeated tests with fluorescently marked fireflies give no evidence that a night of LED lighting drives them away.

Photinus pyralisis a species that normally flickers and flashes around twilight, so they’re used to variable lighting, Firebaugh notes. She’s starting to work with Photuris versicolor fireflies, true creatures of the night. This species may be more sensitive to light.