Life cycles of insects damaged by bright city lights, study finds

OSAKA, Japan — According to a recent study, urban lights and hot city temperatures keep insects awake at night. Artificial light at night can affect all aspect of insect life, not just attracting butterflies to their death around bulbs, Japanese scientists say.

Rats and toads may be able to prey on insects more easily, and lamps may also obscure fireflies’ mating signals. New research on a species of blowfly has shown that many insects change their behavior based on day length, an ability called photoperiodism. Increased nighttime light can disrupt an insect’s photoperiodism to the point that it refuses to enter hibernation.

Scientists from Osaka City and Setsunan Universities conducted experiments indoors and outdoors: In the lab, they mimicked bright urban areas to dark rural areas and tested varying temperatures. They found that the percentage of flies entering hibernation decreased as lighting increased and temperature increased from 15°C to 20°C.

(Credit: Osaka City University)

In the field, the team measured a site where the moon could be seen in clear skies and another in a residential area with streetlights. The percentage of flies entering hibernation in rural areas increased about three weeks earlier than their urban counterparts.

“The study focuses on a species of flesh fly called faux sarcophagusbut the findings could be applicable to any animal species that relies on predictable environmental cues for biological processes such as growth, reproductive behavior, sleep and migration,” says Dr Ayumu Mukai, from Setsunan University. in Japan, in a press release.

“Recognizing the conditions that urbanization brings to insects where they actually live would be a big step forward in mitigating the negative effects,” added Professor Shin Goto, from Osaka City University, “from studies future studies with a variety of insect species at different sites, in cities with different climatic regions would help clarify what levels of light pollution and urban warming affect the seasonal adaptation of insects.

The results are published in the journal Royal Society for Open Science.

South West News Service writer Joe Morgan contributed to this report.