City lights keep insects from hibernation

Everyone knows that city lights are brighter at night compared to rural or undeveloped areas, yet few understand how this affects the creatures who live in the city. A new study in Japan has investigated the impact of city lights and the increased warmth of urban environments on insects. 

While the research was focused on the flesh fly (Sarcophaga similis), study lead author Ayumu Mukai of Setsunan University explained that the results could be applicable to any animal species that relies on predictable environmental signals for biological processes like growth, reproductive behavior, sleep, and migration.

To examine how city lights and the urban environment may affect hibernation in flesh flies, the scientists tested captive flies in the laboratory. Flies were placed under two different light regimes, one mimicking a full moon night, the other similar to an average neighborhood. 

The flies were also subjected to different temperatures, which were similar to average temperatures in October, in both urban (warmer) and rural areas. The scientists found that the flies subjected to warmer and brighter conditions entered hibernation at lower percentage rates than the fly populations exposed to cooler, darker conditions. 

The results were similar in the field. Flies living in warmer environments with bright city lights entered into hibernation later than their counterparts living in more natural habitats.   

Study co-author Shin Goto of Osaka City University explained the potential importance of the research. “Recognizing the conditions urbanization brings upon insects where they actually live would be a great step forward in mitigating any negative effects,” said Goto. 

The scientists are quick to point out that the same impact may not be felt by all insects or in all urban environments and further research is needed. Urban environments and insects are both complex and diverse, but future studies could possibly show us how to create city environments that are more friendly to insect inhabitants. 

The research is published in the journal Royal Society Open Science,

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By Zach Fitzner, Earth.com Staff Writer