Yes, STONEFLY is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, O 1, N 1, E 1, F 4, L 1, Y 4.

Is it a valid word?

STONEFLY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

primitive winged insect with a flattened body; used as bait by fishermen; aquatic gilled larvae are carnivorous and live beneath stones

Also: stone fly.