Light Pollution and Insects: Insect Attraction to Various Types of Residential Lights
Background: The widespread use of electric lamps has created artificial light ecologies and light pollution. The crucial roles played by insects in ecosystems and agriculture may be impacted by their attraction to artificial lights. Previous research has focused on streetlights; little attention has been paid to the more widely used and lower-wattage "area" lights designed for porches, paths, façades, and yards. For such purposes, the basic types of lamps in common use are incandescent, CFL, halogen, LED, and yellow "bug" lights, the latter marketed as reducing insect attraction. The purpose of this study was to compare the potential impact of these various lamps on insect ecologies. Methods: Each night for a summer, one of six types of light bulb was used in a baffle/funnel insect trap. Bulbs were scheduled so that the moon's irradiance was equalized across treatments. Meteorological variables were somewhat equalized by bulb scheduling and otherwise partialled out as covariates. Mean capture rates of total insects and several insect Orders were compared between the bulb types using ANOVA. Results: A total of n = 8887 insects and spiders were captured. The incandescent bulb had the highest capture rate, followed by CFL, halogen, LED with a cool color temperature, and the "bug" light. An LED with a warm color temperature had the lowest capture rate. Similar patterns held for individual Orders. A notable exception was the "bug" light captured significantly more Dermaptera (earwigs) than all other bulbs and significantly more Hemiptera (true bugs) than the warm LED bulb. Conclusions: This is the first study to directly compare all the major types of bulbs designed for exterior residential use. A widespread shift to LED lamps could greatly reduce the impact of light pollution on insects. From an ecological perspective, LEDs with a warm color temperature should be favored because they attract the fewest insects, their lower emission in the blue spectrum should reduce their contribution to light pollution, their directional technology allows for more precise lighting, and they have favorable energy conversions and life cycle assessments.