Citizen science reveals temporally structured insect attraction and mitigation efficacy under artificial light at night

Abstract Artificial light at night (ALAN) is an anthropogenic disturbance with negative effects on nocturnal flying insects, yet most studies treat “night-time” as a uniform exposure period. However, nocturnal insects exhibit pronounced temporal niche partitioning, suggesting that attraction to artificial light and the effectiveness of mitigation measures may vary over the night. Using a citizen science framework, we show how insect attraction along a lakeside road varies across five nightly intervals, comparing conventional high pressure sodium with tailored and shielded LED road lights. Complementary UV ground traps showed marked shifts in local insect abundance and taxonomic composition, with peak attraction occurring during late evening and midnight hours (09.30pm-11.30pm-00.30am). Road lights closely followed this temporal trend. Tailored and shielded LED luminaires reduced total insect attraction, with the strongest effects during peak activity, but limited efficacy during twilight and late-night periods. Both total abundances and taxonomic composition showed significant time-by-treatment interactions, demonstrating that incorporating temporal dynamics can greatly improve targeted mitigation strategies.