This is a fairly widespread insect called the Florida Fern Caterpillar (or Florida Fern Moth), and despite its name, it occurs well into the northern U.S. Boston Fern can be a common host plant, and while caterpillars cause a lot of aesthetic damage and mess, affected plants tend to regrow just fine on their own. You can cut off any unsightly leaves, and can probably shake off many of the caterpillars (it's possible they are largely between generations if you don't find many).

The foliage could be sprayed with a lower-toxicity insecticide containing spinosad to kill any remaining caterpillars as they feed. (Spinosad is absorbed into the foliage, so it won't weather off, though each treatment will only last a few weeks. Follow all product label directions.)

An alternative ingredient to consider using instead is Bacillus thuringiensis kurstaki (B.t.k.), which only affects caterpillars, though it works best on young caterpillars and has reduced to no impact on older caterpillars. (The caterpillar pictured looks fairly mature for this species, but if there are overlapping or successive generations, then a treatment of Bt could be used to prevent another generation from maturing.) Make sure that any Bt product you try using is labeled for caterpillar control, as other strains of Bt (israelensis, for example) are used for mosquitoes or other insects and will not affect caterpillars. Bt is not absorbed into the foliage, so note any label directions about how long to wait before reapplying it, since more than one application may be needed to maintain protection until the end of the growing season.

Miri

Thank you so much. We greatly appreciate it.

You're welcome!