If you live in a city, even if it is small, and you do not have the opportunity to spend a spring or summer night in the natural environment, it is very possible that you have not enjoyed the wonderful image of fireflies for a long time.
Artificial lighting in streets, squares and highways (to give a few examples) is often classified as light pollution and its negative effects on various species have been scientifically proven.
Without going any further, last April the result of a study was published in which a hypothesis was presented that could definitively explain why insects feel fatally attracted to artificial light.
In many species of flying insects, artificial light alters orientation and causes death by burns, exhaustion, or defenselessness against predators.
The potential risks of artificial lighting for a family of coleopteran insects descriptively known as lampyrids (Lampyridae) have also been known for some time; popularly, fireflies or light worms.
A team of researchers from the University of Sussex (United Kingdom) has now delved into the study of the effects of light pollution on specimens of the common European firefly (Lampyris noctiluca) and their data confirm the worst-case scenario.
Estelle Moubarak, Sofia Fernandes, Alan Stewart and Jeremy Niven, signatories of the article showing the results of this study, published in the Journal of Experimental Biology, have been able to demonstrate with data collected in the natural environment and in the laboratory that in In light polluted conditions, male fireflies have great difficulty locating light-emitting females and, consequently, mating and reproduction become increasingly difficult.
The team led by Estelle Moubarak collected fireflies on the South Downs and brought them to her laboratory, where she had prepared a test with a maze that had to be overcome by the males in search of light-emitting females. In reality, the team placed the male fireflies at the bottom of the Y in their test field and a green LED, which mimicked the glow of a female, on top of one of the arms, towards which the male was pointing. than walk.
They then recorded whether the males were following the correct path and how long it took the males to find the fake female.
Next, the researchers repeated the test shining a white artificial light on the maze, with various intensities, from 25 Lux (25 times brighter than moonlight) to 145 Lux (equivalent to light under a street lamp).
While all the fireflies found the LED in the dark, only 70% found the LED in the lowest levels of white light, and only 21% of the insects found their potential mate in the brightest light.
The authors explain that the artificial white light not only affected the firefly's ability to find a suspected female, but also made it take longer for them to reach the LED. In the dark, it took the worms approximately 48 seconds to reach the female-mimicking LED, however it took the same fireflies approximately 60 seconds to reach the LED at the lowest white light levels.
Lighting the maze also caused the male fireflies to spend more time at the bottom of the maze without moving toward a female. In the dark, the insects only spent about 32 s at the bottom of the Y, whereas they spent about 81 s at the bottom of the maze in the brightest conditions.
Moubarak suggests that male fireflies were unable to move toward females when blinded by white light because they cover their compound eyes with a head shield, which acts like a pair of sunglasses, reducing the amount of bright light they see. In fact, when white light illuminated the area with the fake female LED, the fireflies covered their eyes for about 25% of the test, compared to only about 0.5% of the time when the maze was dark. "Keeping the eyes under the head shield shows male fireflies trying to avoid exposure to white light, which suggests that they are very disgusted by it," explains Jeremy Niven in a note released by his university.
