Directions of migrating monarch butterflies (Danaus Plexippus; Danaidae; Lepidoptera) in some parts of the eastern United States.

In September 1977, the directions of 477 migrating monarch butterflies were recorded at five locations in the Eastern United States. The monarchs moved highly directed generally to the southwest, roughly in accordance with the orthodrome direction, to their assumed winter quarter in Mexico. Deviations from the precise direction seemed to be due at least partly to wind drift; major drift required navigational compensation.