Not All Butterflies Are Monarchs: Compass Systems in the Red Admiral (Vanessa atalanta), a European Diurnal Migrant

Abstract

Seasonal migration in animals is a widespread and complex phenomenon, yet the mechanisms underlying orientation and navigation remain poorly understood in many taxa. While significant progress has been made in migratory birds, where multiple compass systems are well described, similar knowledge for migratory Lepidoptera remains limited. Most insights into butterfly and moth orientation come from just two species: the monarch butterfly (Danaus plexippus) and the Australian Bogong moth (Agrotis infusa), both of which possess multimodal compass systems involving visual and geomagnetic cues. However, these species follow unusual migratory strategies that include diapause or aestivation and multigenerational round-trip migrations between breeding region and very specific non-breeding areas, that are not representative of most other Lepidoptera migrants. In contrast, European species such as the painted lady (Vanessa cardui) and red admiral (Vanessa atalanta) undertake regular seasonal migrations involving multiple generations and no diapause, yet the sensory mechanisms guiding their orientation remain largely unexplored. Here, we report findings from a two-year study investigating compass orientation in red admirals using a flight simulator under a range of controlled light and magnetic conditions. Our experiments yielded three key results: (1) red admirals orient using solar cues when selecting migratory direction; (2) the sun compass in this species appears to be time-independent, as clock-shifted individuals did not alter orientation; and (3) there is no sign of magnetic sense in red admirals. These findings sharply contrast with those from monarch butterflies, which rely on both time-compensated sun and light-dependent magnetic compasses. Our results reveal important interspecific variation in compass use among diurnal Lepidoptera and underscore the need to expand orientation research beyond traditional model systems to better understand the diversity of migratory strategies and orientation mechanisms in migratory Lepidoptera.