Low levels of light pollution may block the ability of male glow-worms (Lampyris noctiluca L.) to locate females

Light pollution has been proposed as a factor in the decline of Lampyris noctiluca because it has the potential to interfere with reproductive signaling and has been shown to impact the ability of males to locate light lures in a suburban environment. To compare and test the replicability of this effect in a natural setting and population, imitation females were set out under light polluted and control conditions at varying light pollution intensities in an undisturbed British chalk grassland. Very low levels of light pollution were found to interfere with phototaxis: no males were attracted at either 0.3 or 0.18 lux background lighting versus 33 males collected at paired dark controls. These background illumination levels are much lower than that of 1.5 lux which is recommended by local city councils in Britain to light footpaths. A survey of female L. noctiluca numbers and distribution showed a trend towards female clumping that was not statistically significant. We also found no evidence of light interfering with female signaling behavior.