The longest monarch butterfly fall migration route, from southern Canada to central Mexico, covers how many km one-way? (1 km ≈ 0.6 mi)

Answer

4,800 km

No single butterfly makes the round trip: the ones that fly south to Mexico are a long-lived 'super generation' that survives up to eight months, and the journey back north is completed by several successive short-lived generations of their descendants.

Source: US Forest Service (fs.usda.gov monarch migration page)