Artificial light at night alters feeding behavior of a diurnal caterpillar via effects on host-plant quality
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We investigated potential indirect effects of artificial light at night on diurnal herbivorous insects via effects on host-plant quality. In a series of experiments, we tested the hypothesis that ALAN-induced changes in the growth, nutritional quality or defenses of common milkweed (Asclepias syriaca) would affect the host-plant preferences, feeding frequency, and performance of a diurnal caterpillar, the monarch butterfly (Danaus plexippus). We also tested whether ALAN has direct effects on the feeding frequency or performance of this diurnal herbivore. There was no evidence that ALAN affected the growth, nutritional quality or defensive capabilities of common milkweed, nor were there indirect effects of ALAN on caterpillar preference or performance via effects of ALAN on common milkweed. However, monarch caterpillars directly exposed to ALAN exhibited 58% higher feeding frequency at night and showed a marginally significant 10% increase in pupal mass.