How do you tell the difference between sawfly larvae and moth/butterfly larvae.

From what I’ve read, one way to tell the difference between sawfly larvae and moth larvae is to count the legs. Sawfly larvae have 9 or more pairs of legs - 3 pairs of true legs at the front and 6 or more pairs of stumpy legs (called prolegs) at the back. Butterfly and moth caterpillars never have more than eight pairs of legs (3 pairs of true legs plus up to five pairs of prolegs).

Also sawfly larvae are often seen in clumps eating the same leaf, and wave their heads around when disturbed.