Artificial light at night (ALAN) changes the nocturnal environment encountered by insects, but evidence is distributed unevenly across sensory mechanisms, immediate behavior, life-history traits, ecological interactions, and population outcomes. Treating these levels as interchangeable can exaggerate demographic inference from responses measured over minutes, nights, or single life stages. This scoping review maps peer-reviewed evidence published from 2017 through 2024 concerning insect responses to ALAN, with emphasis on spectral and photoreceptor-related mechanisms, attraction and orientation, temporal disruption, feeding and reproduction, predator–prey interactions, and population-level evidence. Exposure was treated as multidimensional, including spectral composition, illuminance, spatial configuration, duration, temporal modulation, and background skyglow where reported. Experimental and field studies show that artificial illumination can disrupt flight orientation, alter attraction, interfere with bioluminescent communication, shift circadian or seasonal responses, modify diapause and reproduction, and reorganize ecological interactions. Effects are strongly conditional on taxon, life stage, spectrum, intensity, timing, ecological context, and measurement scale. Short-term aggregation or behavioral change cannot by itself establish population growth or decline. The review proposes a cross-scale inferential distinction separating sensory response, immediate behavior, individual performance, ecological interaction, local redistribution or abundance, and demonstrated demographic change. This distinction clarifies where mechanistic evidence is strong and where population inference remains weak. Progress requires longitudinal designs that connect exposure architecture and mechanism to survival, reproduction, recruitment, dispersal, and abundance at biologically relevant spatial scales.
