Gentle or devastating light? The impact of urban light on nocturnal insects

Moths, Antheraea polyphemus and Automeris io, night photography.
Credit: Insectarium de Montréal (Maxim Larrivée)
Papillons nocturnes
Gentle or devastating light? The impact of urban light on nocturnal insects

Darkness has given way, over the great evolution of human beings, to nocturnal landscapes of manmade light. Those lights provide humans with safety. Seen from space, the Earth is alive with lights. But behind the scenes, nature is being altered to its very essence.

Light and living things

As the days go by, living beings alternate, as though in a dance whose rhythm is controlled by the rising and setting of the celestial bodies. That play of light determines life by controlling biological processes. Thus, some animals are diurnal, while others are nocturnal.

A modification to these conditions can disorder flora and fauna. Especially sensitive to variations in the environment, nocturnal insects are among the animals most affected by this phenomenon.

Devastating effects of light pollution

Changes in ambient light impair circadian rhythms, the 24-hour biological cycles that regulate hormonal, behavioral and physiological processes such as the state of being awake, hatching and migrations. For some beetles, mayflies, moths and other insects, light emissions break up landscapes and thus reduce access to food or to sexual partners. They also disrupt animal communities by modifying the relationships between different species (predators and prey, for example) or between individuals of the same species.

Why are nocturnal insects attracted by artificial light?

It might seem ridiculous for an insect to fly tirelessly around a light source, only to end up burning itself to death or dying of exhaustion. But that phenomenon can be explained. Insects possess an inner compass that guides them in the dark based on the position of the Moon. When it substitutes for that, artificial lighting disorients insects, who no longer know which direction to take. According to a Swiss study, every streetlight kills 150 moths daily, which corresponds to a loss of billions of insects a year!


The light pollution that gains ground year after year affects the world’s biodiversity and beauty. Fortunately it’s possible to reduce those emissions by using more efficient lighting. In big box stores it’s easy to find “anti-insect” bulbs; these give off a yellow light that doesn’t attract insects. It’s also recommended to turn off all non-essential lighting. Insects and the environment will both be much better off!

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