Altitudes attained by migrating monarch butterflies, Danaus p. plexippus (Lepidoptera: Danaidae), as reported by glider pilots

Glider pilots at four different locations in North America have observed D. plexippus flying at altitudes ranging from 600 to 1250 m. Three of the observers reported that the butterflies were soaring in thermals, and one observer reported that they occasionally enter clouds.