From skylight cues to magnetic fields: the toolkit of insect long-distance navigation.

Despite their tiny size, lepidopterans accomplish some of the most extraordinary migrations on Earth. Monarch butterflies and bogong moths, for example, travel vast distances to find the same seasonal sheltering sites year after year, and remarkably do so without any prior experience. How do these delicate creatures navigate so precisely across large and changing landscapes? Scientists have spent decades unraveling this mystery, revealing that lepidopterans possess a sophisticated suite of navigational tools that rival those of much larger animals. Lepidopteran compass systems rely on celestial cues like the sun, stars, and polarized light, as well as the Earth's magnetic field. Diurnal monarchs and nocturnal bogong moths have become model species for understanding how insects combine skylight and magnetic compasses to find their way. Recent discoveries have shed light on the neural circuits and genetic blueprints that power these compasses. In this review, we provide an overview of the navigational toolkit employed by lepidopteran migrants, dive into their mechanisms, and highlight future directions needed to fully decode the secrets of insect long-distance navigation.