World News | Light pollution is robbing fireflies of mating sparkle

London, June 14 (talk) The invention of the electric light extended our lives into the deeper nights: streetlights help us travel outdoors more safely, while indoor lighting allows us to work and play longer. The entire stadium is flooded with lights so people can watch games at night. Even your garden might be illuminated to accentuate its more delicate features.

However, light produced outside of the natural cycles of the sun and moon can have unwanted effects, which is actually a form of pollution. Like other species, light pollution can harm animals, especially nocturnal animals. Some predators that would otherwise be present during the day now choose to hunt after dusk and disrupt entire food webs.

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Artificial light at night can have particularly severe consequences for insects. Moths, for example, who were distracted by the lure of street lighting in large numbers neglected their nocturnal pollination duties, could have serious consequences for the wider ecosystem, according to one study.

How some insects respond to sudden brightening of their nocturnal habitats remains poorly understood. The common firefly (Lampyris noctiluca) is another nocturnal insect that uses bioluminescent signals during mating. Female fireflies stay put and use a chemical reaction to produce green bioluminescence in their abdomens, attracting flying males.

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Several field studies have shown that white light, similar to that produced by modern LED street lighting, can reduce the number of males trying to find females. My research team and I wanted to figure out what was going on, so we brought firefly mating into the lab.

We collected male fireflies from the grass near the laboratory. Upon returning to the laboratory, we transferred each male animal to a Y-shaped maze in the dark. One arm of the maze contains a green LED that acts as a virtual female. After the LED is turned on, the male will usually scurry towards the light. We then turned on a light simulating artificial lighting at night and repeated the experiment.

In the dark, males can easily find false females. But under the dimmest white light we use, which is roughly equivalent to street lighting, only 70 percent of men found green LEDs. This drops to 21% at the brightest light level, which is equivalent to the lighting used to illuminate town squares and monuments in parks.

Composite image of a firefly on wood in bright light and a green glowing abdomen in the dark.

Monitoring male fireflies in the Y-maze allowed us to examine their behavior in detail. White light increased the time it took them to reach the dummy females: about 48 seconds for the males in the dark, and about a minute under the lowest level of white light.

blinded by light

We also noticed that when males were exposed to white light, they lingered before entering one of the arms. The males spent an average of just 32 seconds at the bottom of the Y-maze in the dark, but this increased to 81 seconds under the brightest white light.

This hesitation may be due to the dazzling fireflies. When the insects were exposed to white light, their heads and compound eyes retracted beneath the shield-like structure on the top of the head. In the dark, the males kept their heads under the blindfold for just 0.5 percent of the trial duration — this rose to 25 percent under white light. More than half of the males kept their heads covered throughout the light trial.

Beetles on plant stems.

We think of the hood as a pair of sunglasses, reducing the amount of light that reaches the eyes. This may not be enough to protect them from white light, though, as males with their heads retracted seem less likely to approach dummy females. This suggests that artificial lighting at night can deter males from seeking out females, not only because it makes potential mates’ bioluminescent signals harder to spot, but also because they put them in stasis.

These detailed experiments on insect behavior contribute to our understanding of what fireflies experience at night due to artificial lighting, complementing ecological research conducted in this field. Both pieces of evidence tell us that reducing light pollution — by putting shades on streetlights or changing the wavelength of the light they emit — could help insects live at night while we go about our lives. (dialogue)

(This is an unedited and auto-generated story from a Syndicated News feed, the body of content may not have been modified or edited by LatestLY staff)