Did you notice that moths or other flying insects were circling around a bulb? Why do they do that? Why do they Gather Around Lights? This has been a mystery for centuries. Many people thought that,

  1. Moths or flies are attracted to light, thinking it is the moon or using it for navigation and to understand the direction.
  2. The heat or the lights attracted them. 
  3. The heat or lights confused their vision system.

However, new research published in Nature Communications showed us a different explanation supported by experiments and real-time data (Baker et al., 2024). A team of researchers conducted both lab experiments and observations.

What They Found

Surprisingly, the moths don’t actually fly straight into the light. Instead, they turn their backs (called the “dorsum”) toward the light source. This behavior is part of a natural reflex called the dorsal-light response (DLR). In nature, moths and other flies use the sky’s brightness to keep their body balanced during flight. They usually turn their back toward the bright sky to keep their body straight while flying.

But when the bright light is coming from below or the side, this reflex causes them to turn in the light's direction. During this time, they usually follow three pathways to fly. Those are:

  1. Orbiting: circling around the light source.
  2. Stalling: flying slowly, sometimes spiraling.
  3. Inverting: flipping upside-down and crashing.

So, they’re not going toward the light because they want to. They’re just getting confused by where the light is coming from.

Figure1. Flight paths of moths in response to artificial light (Baker et al., 2024). Reprinted from Nature Communications, 15, Article 44785, by C. J. Baker, D. F. Pavan, J. Leclercq, L. J. de Vries, C. H. Ferreira, J. K. Dominiak, ... & S. T. Fabian, 2024, https://doi.org/10.1038/s41467-024-44785-3. © The Author(s) 2024, under a Creative Commons CC BY 4.0 license.

Figure 2. Flight paths of moths in response to artificial light (Baker et al., 2024). Reprinted from Nature Communications, 15, Article 44785, by C. J. Baker, D. F. Pavan, J. Leclercq, L. J. de Vries, C. H. Ferreira, J. K. Dominiak, ... & S. T. Fabian, 2024, https://doi.org/10.1038/s41467-024-44785-3. © The Author(s) 2024, under a Creative Commons CC BY 4.0 license.

This discovery helps us understand a very common—but misunderstood—animal behavior. It also shows how artificial lights have a negative impact on insects, which can even lead to death. This knowledge and understanding are necessary because insects help with pollination (which is crucial for plants to reproduce) and they are also a big part of the food chain.

References

  1. Baker, C. J., Pavan, D. F., Leclercq, J., de Vries, L. J., Ferreira, C. H., Dominiak, J. K., ... & Fabian, S. T. (2024). Why flying insects gather at artificial light. Nature Communications, 15(1), Article 44785. https://doi.org/10.1038/s41467-024-44785-3
  2. Mazokhin-Porshnyakov, G. A. (1960). Why insects fly to light by night. Revue d’Entomologie de l’URSS, 39(1), 52–58.
  3. Sotthibandhu, S., & Baker, R. R. (1979). Celestial orientation by the large yellow underwing moth, Noctua pronuba L. Animal Behaviour, 27, 786–800. https://doi.org/10.1016/0003-3472(79)90010-1
  4. Callahan, P. S. (1965). Far infra-red emission and detection by night-flying moths. Nature, 206, 1172–1173. https://doi.org/10.1038/2061172a0
  5. Robinson, H. S., & Robinson, P. J. (1950). Some notes on the observed behaviour of Lepidoptera in flight in the vicinity of light sources. Entomologist’s Gazette, 1, 3–15.
  6. Hsiao, H. S. (1973). Flight paths of night-flying moths to light. Journal of Insect Physiology, 19, 1971–1976. https://doi.org/10.1016/0022-1910(73)90182-8