Historical behavioural data disentangle evolutionary and environmental drivers of recent declines in insect attraction to light

Authors: CHAN, WEI-PING - Harvard University; DASZAK, IMOGEN - Northeastern University; BUNTIN, GEORGE - University Of Georgia; COOK, DON - Mississippi State University; CROW, WHITNEY - Mississippi State University; HUANG, FANGNENG - Louisiana State University; HUSETH, ANDERS - Michigan State University; KESHEIMER, KATELYN - Bayer Cropscience; Ludwick, Dalton; PAULA-MORAES, SILVANA - University Of Nebraska; REISIG, DOMINIC - North Carolina State University; OWENS, AVALON - University Of Nebraska

Submitted to: Proceedings of the Royal Society. B. Biological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2025
Publication Date: 12/17/2025
Citation: Chan, W., Daszak, I., Buntin, G.D., Cook, D., Crow, W., Huang, F., Huseth, A., Kesheimer, K., Ludwick, D.C., Paula-Moraes, S.V., Reisig, D., Owens, A.C. 2025. Historical behavioural data disentangle evolutionary and environmental drivers of recent declines in insect attraction to light. Proceedings of the Royal Society. B. Biological Sciences. 292(2061). https://doi.org/10.1098/rspb.2025.2319.
DOI: https://doi.org/10.1098/rspb.2025.2319

Interpretive Summary: The world has focused on insect declines as a concern for world health. To understand whether insect populations are truly declining or just less responsive to lights, a team investigated this hypothesis with a major pest of many crops, the corn earworm (Helicoverpa zea). Historical data on this insect's attraction to light did not differ from modern evaluations conducted in the 2020s. This suggests the insect has not become less responsive to light. Instead, it was discovered that the insect may be less commonly found at lights due to increases in light abundance as well as intensity. The authors suggest that light traps used to monitor insects may be less effective and falsely indicating a decline, though this is a working hypothesis and not concrete evidence.

Technical Abstract: Entomologists monitor insect population trends by surveying individuals attracted to artificial lights at night with the assumption that flight-to-light behaviour is fixed. However, emerging data suggest that entomological light traps are rapidly losing efficacy relative to other trap types, and the dramatic growth in anthropogenic light pollution over the past century has been identified as a probable cause. To investigate whether decades of strong selection against a conspicuously maladaptive behaviour have decreased insect attraction to light and compromised light trapping as a survey method, we compared the light attraction of urban and rural Helicoverpa zea (Boddie) corn earworm moths with historical behavioural records from 1967. Our results suggest that the flight-to-light response has remained relatively constant over time but may be strongly influenced by environmental visual clutter even in seemingly dark habitats. These findings call into question the use of light traps in long-term surveys, as the darkness within which they operate is rapidly deteriorating.