Diversity of swimming behavior in larval Lepidoptera.

Lepidoptera are a highly diverse lineage of predominantly terrestrial insects, yet their larvae occupy diverse habitats where they may experience unexpected contact with water or accidental submersion. Such exposure may have favored adaptations that enable terrestrial lepidopteran larvae to survive underwater for short periods. Using a combination of personal and crowd-sourced observations, we document a striking diversity of behaviors displayed by Lepidoptera (32 species across 16 families) when suddenly exposed to water. This includes swimming, which we observed in 4 lepidopteran families. We developed a behavioral ontology comprising 9 distinct behaviors and 5 non-directional behaviors, each observed on the water surface. Our study highlights a largely overlooked dimension of Lepidoptera biology and establishes a framework for future research on the significance of this behavior.