Not all butterflies are monarchs: orientation using daytime celestial cues but not magnetic cues in European migratory red admirals ( Vanessa atalanta )

Abstract

Seasonal migration in animals is a widespread and complex phenomenon, yet the mechanisms underlying orientation and navigation remain poorly understood in many taxa. In Lepidoptera, most insights come from monarch butterflies (Danaus plexippus) and Australian bogong moths (Agrotis infusa), which use both visual and geomagnetic cues for orientation. However, these species undertake multigenerational round trips between breeding grounds and specific non-breeding areas and are, therefore, not representative of most other lepidopteran migrants, for which the sensory mechanisms guiding orientation remain largely unexplored. Here, we report findings from a 2-year study investigating orientation mechanisms in the red admiral (Vanessa atalanta), a European migratory butterfly, under controlled light and magnetic conditions. Our results demonstrate that (i) red admirals primarily rely on solar cues for selecting their migratory direction; (ii) they show no response to clock-shift manipulation; and (iii) there is no evidence of magnetic compass use. These findings contrast with monarch butterflies, which rely on both a time-compensated sun compass and a light-dependent magnetic compass, and reveal interspecific variation in compass use among diurnal Lepidoptera. This underscores the need to expand orientation research beyond traditional model systems to better capture the diversity of migratory strategies and orientation mechanisms across Lepidoptera.