Where to Find and Catch Scatterbug
From Pokemon Go Wiki
Scatterbug are found and captured in Nest and Habitat locations.
Nests
Scatterbug Nests are locations that consistently spawn Scatterbug.
Habitats
Scatterbug Habitats are spawn locations where Scatterbug is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: