[bigjim5589]

Generally, nymphs imitate that phase in aquatic insects lives, the nymphal phase, while wet flies may imitate nymphs or other insects, or they could imitate other things a fish may eat, even possibly small baitfish. Although, there is quite a bit of overlap, and there are many patterns now that could be classified as either, or. I believe, that it's probable, that early wet fly patterns were attempts at imitations of naturals, but the materials available or even the science available may have limited how exact they ended up as actual imitations. Nymphs are later developments as both materials & information about aquatic insects became available.