The Light Trap
If you live in the mountainside or countryside, when you turn on the lights at night, it will always attract insects to circle around them. This phototaxis of insects can indeed be quite bothersome! Some people are troubled with how to solve this problem. However, coming from a different perspective, could it be that the lights of the city are actually harming nature's insects...
The scientific community has been studying the reasons for insect phototaxis for many years, but there is still no definitive conclusion. Some hypotheses have suggested that many nocturnal insects use luminous celestial bodies as reference points for navigation, and the lights at night are misleading them into thinking the lights are reference points, causing them to fly towards the light source.
Others hypothesise that the far infrared emitted by the lights is similar to the vibrational spectrum of chemical molecules released by insects to attract the opposite sex, causing them to mistakenly believe the emission is a mating signal from the opposite sex, and thus, they rush towards the light.
Yet another hypothesis is that nocturnal insects are accustomed to dark environments, and the brightness from the lights is too dazzling for them, disrupting their navigation system, and making it difficult for them to fly properly.
Regardless of which hypothesis, it is clear that insects are actually victims of artificial light sources!
Lights Can Lead to Extinction
On an ecological level, as insects are attracted to light and fly around it, the lights become an "ecological trap" that exposes the trapped insects to predators, making them more vulnerable as prey. Even if they are not caught by predators, they may be trapped by the light source and eventually die from exhaustion.
Fireflies are even more sensitive to light, as they use light as a mating signal. Fireflies emit light as a signal for mates, and overly bright lights can overshadow these signals, making it difficult for them to successfully mate and reproduce. In 2020, the Highways Department installed streetlights at Tei Tong Tsai, Lantau Island, which led to the near extinction of the Chenghoiyan Ototretine firefly (Oculogryphus chenghoiyanae) that inhabited the area, serving as a painful lesson.
Lights not only reduce the number of individuals of insect populations in the wild, they can even affect the survival of the entire population. This, in turn, affects ecological processes such as the food chain and pollination, with far-reaching consequences.
Making Lights Insect-Friendly
In recent years, insect-friendly outdoor light sources have begun to appear on the market. In comparison to traditional light sources, these insect-friendly light sources use special spectra and also have lower light intensity, minimising attraction and disturbance to insects. However, these insect-friendly light sources are not yet widely available.
There are actually some simple measures that can already reduce the impact of light on insects. For example, in the use of outdoor lighting, the most important principle is to rethink the necessity for night-time lighting and to abandon the "brighter is better" mentality, adjusting the intensity to just what is needed; or to abandon the "more is better" mentality, and installing lighting equipment only where necessary.
In addition, we can install timers to turn on the lights only when needed, or add lampshades to reduce scattering and to direct the light source only to the required ground areas.
It is even simpler for indoor lighting. We just need to draw the curtains to prevent indoor lighting from illuminating the outdoors, and then install window screens which will greatly reduce the chance of insects entering the house due to the light!