NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 28 3.5.1.1 Effects on Insects and Other Arthropods Mechanisms by which insects are affected by and respond to artificial light sources are summarized by Desouhant et al. (2019). The authors discuss effects on population dynamics and community composition and functioning. Also discussed are evolutionary changes due to selective pressures created by artificial light. Insects and other arthropods use visual information to navigate, find food, and avoid predators. As previously noted, moths and many other nocturnal insects are attracted to lights, and billions of insects die as a result. Why insects are attracted to light sources is unclear. However, it appears to affect their night vision and ability to orient and navigate (Schroer and Hölker 2016). Research shows that the composition of invertebrate communities within the vicinity of streetlamps is affected, and with that, numbers of predator and scavenger species on the ground nearby also increases in response to increased numbers of prey (Davies et al. 2012). Research also shows that artificial light at night affects development, survival, and reproduction in some types of insects, particularly when the source contains blue or ultraviolet (UV) wavelengths (Schroer and Hölker 2016), and as previously noted, these wavelengths are particularly attractive to certain species. Several studies show the effects on moths. Certain types of moths exhibit reduced mating success (van Geffen et al. 2015a). Artificial light at night can also interfere with pollination (Macgregor et al. 2017); reduce feeding time in several species of moths (van Langevelde et al. 2017); negatively affect pheromone production (van Geffen et al. 2015b); and disrupt initiation of diapause and cause other life cycle changes (van Geffen et al. 2014). Van Langevelde et al. (2018) identified artificial light as an important driver of declines in the abundance of various moth species that are attracted to it. Artificial light at night can mask bioluminescence from fireflies, interfering with communication essential for successful reproduction. It also affects niche partitioning, resulting in different firefly species being active at the same time, bringing them into competition that would not otherwise occur. Artificial light at night can suppress melatonin levels in a species of cricket, negatively affecting their immune systems (Durrant et al. 2015). Very low levels of artificial light can affect predator avoidance behavior in aquatic insects (Bishop 1969) and the upward and downward movement of other aquatic invertebrates in response to light levels, which may affect predation on these and other species (Moore et al. 2000). Evidence suggests that artificial light at night may in some cases be an evolutionary driver for certain insect species. Altermatt and Ebert’s (2016) study of “flight to light” behavior in ermine moths suggests that moths from light polluted urban environments have evolved over the course of several decades to show less attraction to lights compared to moths from naturally dark areas. Insect responses to artificial light and evolutionary influences may create indirect effects on other species. For example, many animals prey on the swarms of insects drawn to lights (Davies et al. 2012), including birds, bats, frogs and toads, spiders, and other insects. While these species may benefit from the easy access to prey, the abundance of the prey species is reduced, which in turn may reduce the availability of food for other species. Knop et al. (2017) found there is reduced visitation Flying insects attracted to a light source at night. C.G.P. Grey
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