Yes, DIPTERANS is a Scrabble word!

Letter values in Scrabble US: D 2, I 1, P 3, T 1, E 1, R 1, A 1, N 1, S 1.

Is it a valid word?

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

insects having usually a single pair of functional wings (anterior pair) with the posterior pair reduced to small knobbed structures and mouth parts adapted for sucking or lapping or piercing

Also: dipterous insect, two-winged insects.