Abstract
Transparency reduces prey detectability by predators. While the proportion of transmitted light in aquatic species is higher as light availability increases, less is known about such variation in terrestrial species. Transparency has evolved several times in the typically opaque winged Lepidoptera order (moths and butterflies), displaying a large diversity of degrees. Using two complementary approaches, we explore how the evolution of the differences in light transmittance relates to habitat openness, daytime activity and mimicry syndrome (bee/wasp versus dead-leaf mimic). First, by exposing artificial moth-like prey to wild avian predators in open and closed habitats, we show that survival increases at higher proportions of transmitted light in open habitats. Second, by analysing the evolution of wing features and ecological traits in 107 clearwing species, we confirm that diurnal open-habitat species show higher light transmittances than diurnal closed-habitat species. Additionally, bee/wasp mimics are more often diurnal and have higher and less variable light transmittances than dead-leaf mimics, which are more often nocturnal. Bright conditions, such as open habitats during the day, and mimicry of insects with transparent wings seem to promote high light transmittance. Habitat openness, daytime activity and species interactions play a crucial role in determining transparency design.
Competing Interest Statement
The authors have declared no competing interest.