Where to Find and Catch Mothim
From Pokemon Go Wiki
Mothim are found and captured in Nest and Habitat locations.
Nests
Mothim Nests are locations that consistently spawn Mothim.
Habitats
Mothim Habitats are spawn locations where Mothim 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: