Current evidence in support of insect-friendly lighting practices

Anthropogenic light pollution is an emerging threat to natural ecosystems with myriad effects on insects in particular. Insect conservationists are increasingly interested in mitigating this driver of insect declines via sustainable lighting practices. Current recommendations often follow the five principles for responsible outdoor lighting developed by DarkSky International, a non-profit organization founded by astronomers. While these principles unquestionably increase star visibility, their ecological costs and benefits remain relatively unexplored. Herein we review recent research into the effects of each principle on insect fitness broadly defined. Most studies test the efficacy of spectral tuning, followed by dimming, although both mitigation methods seem generally ineffective in practice. In contrast, both shielding and motion detectors show promise as mitigation methods but remain remarkably understudied. Nonetheless, a preponderance of evidence now demonstrates that removing unnecessary light sources from natural habitats can reverse their varied impacts on diverse insect taxa and greatly benefit insect conservation

Artificial light impacts the mate success of female fireflies

Anthropogenic light pollution is a novel environmental disruption that affects the movement, foraging and mating behaviour of nocturnal animals. Most of these effects are sublethal, and their net impact on reproductive fitness and population persistence is often extrapolated from behavioural data. Without dedicated tracking of wild individuals, however, it is impossible to predict whether populations in light-polluted habitats will decline or, instead, move to shaded refuges. To disentangle these conflicting possibilities, we investigated how artificial light affects mating and movement in North American Photinus, a genus of bioluminescent fireflies known to experience courtship failure under artificial light. The degree to which artificial light reduced mate success depended on the intensity of the light treatment, its environmental context, and the temporal niche of the species in question. In the laboratory, direct exposure to artificial light completely prevented mating in semi-nocturnal Photinus obscurellus. In the field, artificial light had little impact on the movement or mate success of local Photinus pyralis and Photinus marginellus but strongly influenced mate location in Photinus greeni; all three species are relatively crepuscular. Our nuanced results suggest greater appreciation of behavioural diversity will help insect conservationists and dark sky advocates better target efforts to protect at-risk species

Data from: The impact of artificial light at night on nocturnal insects: a review and synthesis

In recent decades, advances in lighting technology have precipitated exponential increases in night sky brightness worldwide, raising concerns in the scientific community about the impact of artificial light at night (ALAN) on crepuscular and nocturnal biodiversity. Long-term records show that insect abundance has declined significantly over this time, with worrying implications for terrestrial ecosystems. The majority of investigations into the vulnerability of nocturnal insects to artificial light have focused on the flight-to-light behavior exhibited by select insect families. However, ALAN can affect insects in other ways as well. This review proposes five categories of ALAN impact on nocturnal insects, highlighting past research and identifying key knowledge gaps. We conclude with a summary of relevant literature on bioluminescent fireflies, which emphasizes the unique vulnerability of terrestrial light-based communication systems to artificial illumination. Comprehensive understanding of the ecological impacts of ALAN on diverse nocturnal insect taxa will enable researchers to seek out methods whereby fireflies, moths, and other essential members of the nocturnal ecosystem can coexist with humans on an increasingly urbanized planet

The impact of light pollution on the visual ecology of Aquatica ficta (Coleoptera: Lampyridae)

The majority of fireflies in Taiwan communicate with conspecifics via the exchange of bioluminescent signals. The characteristic courtship signals of different species have been well described, yet we know little about the ways in which environmental conditions can affect signaling behavior. The impact of anthropogenic light pollution is of particular interest, as it must contribute some noise to the signal transmission milieu. Herein we explore the ways in which a local species, Aquatica ficta, reacts to environmental light. We expose larval Aq. ficta to low levels of artificial night lighting over two weeks, then analyze their RNA transcriptome expression. We also expose adult Aq. ficta to LED pucks of varying wavelength and intensity, while observing the intensity and frequency of flash signals produced by specimens under these conditions. The transcriptomes of larval specimens exposed to artificial night lighting indicated a significant stress response. Adult Aq. ficta exposed to wavelengths at or below 533nm produced flash signals of greater intensity with diminished frequency; no significant behavioral changes were observed during exposures to wavelengths at or above 597nm. Whether the plasticity of firefly signaling behavior is sufficient to ensure successful transmission of courtship signals remains to be seen. If Aq. ficta are unable to compete with growing levels of anthropogenic light pollution, their reproductive rates will be greatly reduced. Therefore, the action spectra produced by this study should be used to inform decisions about the types of street lamps to be placed near firefly habitats; such consideration will minimize the impact of anthropogenic light pollution on the rich biodiversity and thriving ecological tourism industry of Taiwan

Aquatica_ficta

This .zip contains eight 32 minute recordings of Aquatica ficta alarm flash intensity, each accompanied a key that indicates the condition of the ambient light environment during this time

Average peak intensity and frequency of light signals produced by <i>A</i>. <i>ficta</i> under exposure to varying wavelengths and intensities of ambient light.

<p>Average peak intensity and frequency of light signals produced by <i>A</i>. <i>ficta</i> under exposure to varying wavelengths and intensities of ambient light.</p

Effects of exposure wavelength and intensity on firefly flash morphology.

<p>Change in average (± 1 SE) flash intensity (A) and frequency (B) of light signals emitted by <i>A</i>. <i>ficta</i> under illumination by eight wavelengths and two intensities of ambient light (N = 6). Base values for average flash intensity (5420 counts) and flash frequency (43.167 peaks/min) obtained from 1 min dark recordings have been subtracted out.</p

Plastic effects of 533 nm ambient light exposure on firefly flash morphology.

<p>(A) Example of change in intensity of flashes emitted by <i>A</i>. <i>ficta</i> male under different illumination conditions (indicated above each section), recorded in units of average counts per 100 ms over 4 min. (B) Changes in signal intensity over 4 min of separate <i>A</i>. <i>ficta</i> male under the same illumination conditions (indicated above each section).</p