Artificial light makes it difficult for male fireflies to find bright females, with potentially disastrous consequences for the reproduction of future global firefly populations. This was demonstrated in a study by the University of Sussex, published in the Journal of Experimental Biology.

The bright lights of big cities are wonders of the modern world, meant to help us work, stay safe and enjoy the world around us after dark. While artificial light has proven to be a great tool for increasing human productivity, some nocturnal animals, and even people, pay a price for this illumination.

Light pollution affects many animals. Female common fireflies (Lampyris noctiluca) emit a green light from their abdomen to attract males in flight, but are unable to fly to new locations to escape light pollution. After collecting the fireflies from the South Downs in the UK, Estelle Moubarak, from the University of Sussex in the UK, transported them to the laboratory, before beginning the difficult task of transferring the male insects into a Y-shaped maze, devoid of artificial light.

The team of researchers placed the male fireflies at the base of the Y and a Light Emitting Diod (LED) device – solid-state lighting that generates light using semiconductors rather than a filament or gas – at the top of one of the arms, towards which the male had to walk, mimicking the female’s glow. They then recorded whether and how long it took the males to find the fake female.

Then, the scientists switched on a white light above the maze, which ranged from 25 lux, 25 times brighter than moonlight, to 145 lux, the equivalent of the light of a street lamp. While all the fireflies found the Light Emitting Diod (LED) in the dark, only 70 per cent found the Light Emitting Diod (LED) at the faintest levels of white light and only 21 per cent of the insects found the potential mate in the brightest light.

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