A major compass system that monarch butterflys use for directional information for long distance migration is a time-compensated sun compass. The sun compass involves the eye’s sensing of skylight cues for direction and the brain integration of skylight-induced neural responses in the central complex, the presumed site of the sun compass in brain. Sun compass allows flight direction to be constantly adjusted to keep flying south. The genome of butterfly is just completed and specific expansion of chemoreceptors was found and may relate to Sun compass directed long distance migration.