Female moths call in vain: Streetlights diminish the promise of mating

Abstract Artificial light at night has increased significantly in recent decades, profoundly impacting moths, which are key contributors to pollination networks. The global shift to light‐emitting diode (LED) streetlights has further transformed the nocturnal light environment, especially because of their high variability in spectrum and intensity. However, the impact on moths' mating success remains poorly understood, highlighting the urgent need to investigate their behavioural responses. We recorded the flight behaviour of male moths ( Sphinx ligustri L.) using a symmetrical flight tunnel. Two different light environments, homogeneous and heterogeneous, with a female positioned on one side of the tunnel, were used to test in different combinations the effect of LEDs (Amber, Warm white and Neutral white) and intensities (0.05, 150, 370 and 590 lux) on arrival location, flight duration and direction changes of males. In a homogeneous light environment, all tested LEDs significantly reduced the arrival frequency of males at the females compared with a dim light condition, demonstrating that streetlight negatively affects encounter rates. However, neither flight duration nor direction changes were significantly affected. In a heterogeneous light environment, the highest proportion of males was able to reach the females in the presence of Warm white (2200 K), indicating that Amber (1800 K) may not be a universal solution for mitigating the negative effects of artificial light. Both flight duration and direction changes were significantly reduced for Neutral white (3900 K) compared with Warm white, concluding that this LED type induced fast and directed flights towards the light source. Interestingly, light intensity did not significantly affect any of the analysed parameters. Statement of significance: The presence of light drastically reduced the probability of males reaching the females. Furthermore, LEDs with the lowest correlated colour temperature (CCT) were not the ones leading to the highest promise of mating success, indicating that the spectrum of an LED might have an optimum. As LED efficiency decreases with lower CCT values this finding is of crucial importance when considering the indirect effects of light pollution, such as the CO 2 footprint, when developing lighting strategies as minimally disruptive as possible.