Moths are strongly attracted to ultraviolet and blue radiation

Abstract We carried out three choice experiments with 6116 nocturnal lepidopteran individuals (95 species, 7 families, 32?075 counts), each replicated 105 times during the seasons of 2?years. Moths were released indoors at the centre of a 10???10?m area with different lamps placed at each corner. In experiment 1, lamps emitted ultraviolet (UV) (peak at 365?nm), blue (450?nm), green (520?nm) or cool white (450 and 520?nm) radiation. In experiment?2, UV was replaced by red (640?nm). In experiment?3, we used UV and three mixed radiation lamps of different emission intensities (365?520?nm). We applied a linear mixed effect model to test for differences in attraction to the light sources. Among all counts, 12.2% (males) and 9.2% (females) were attracted to a lamp. Among the lamp counts, 84% were made at the UV lamp in experiment?1. In experiment?2, 63% of the counts were made at the blue lamp. In experiment?3, most counts were made at the strongest mixed radiation lamp (31%), and the UV lamp (28%). Patterns were generally similar across Lepidopteran families, and for both sexes. Moths are clearly preferentially attracted to short-wave radiation. Even small quantities of UV radiation, emitted, for example, by metal halide lamps and certain mercury vapour tubes, will disproportionately contribute to light pollution. Since blue light also attracts moths strongly, lamps with a low proportion of blue light should be given priority in lighting planning.