If hoppers develop in very dense populations they become more gregarious. Monarch butterflies - Adults migrate from North America in the fall to overwinter in Mexico. Some survive until the following Spring and breed. Birds - numerous examples. Most of what we know about migration comes from work done with birds.
Animals use a variety of redundant mechanisms to find their way around.
This is called clock-shifting . Classic experiment by Steve Emlen -Indigo Buntings hand raised without being able to see the sky were unable to orient during migration. Not only did Emlen show that Indigo Buntings used celestial cues for migratory orientation, but his experiment also showed that learning was involved in this process.