LEWISBURG, Pa. — Late July is one of the best times in the Northern Hemisphere to view the nightly natural light show produced by fireflies. But unless society turns off the increasing artificial lighting, you may see fewer fireflies, which are “blinking out” from all that light pollution.
“Light at night harms fireflies,” Lower says. “They use light to communicate, and their light is a mating signal. So if there’s a lot of ambient light around, they can’t see each other’s signals, and they can’t find each other to mate.”
The fireflies we see in the summer are adults, according to Lower. Most species only have a span of about two weeks to find a mate and lay eggs. During the rest of the year, the eggs hatch into larvae and grow until summer. Some fireflies have two-year life cycles, “so many of the fireflies we are seeing right now first hatched out of eggs in the summer of 2018,” Lower says.
An important part of this mating process is for a firefly to light up and use a blinking pattern to attract a mate. Sometimes, fireflies use a blinking pattern in unison to literally light up the path to find a mate.
“An individual male has greater reproductive success in finding a female if they all signal together,” says Lower. “In Malaysia, where all of the males gather together and signal from a single tree, we think that is to identify a specific area where females know to go and mating can occur.” This synchronicity gives fireflies a higher chance to mate and lay eggs.
In order for people to attract fireflies to their yard, Lower says they should “keep their lights off in order to minimize light pollution, make sure that there are spaces provided for their prey such as worms and slugs, and develop areas with vegetation to provide cover and moisture for the fireflies during the heat of the day.”
Lower discussed more “cool things” people never knew about fireflies in this Scientific American article.