1a.  Less than 5 mm long, 'hairy', two dense brushes of setae projecting from rear end.
                Polyxenida
 
1b.  Generally >5 mm long; if 'hairy', without brushes at rear.
                Go to 2

2a.  Body about half as wide as long, strongly convex on top; animal can curl into a ball.
                Sphaerotheriida
 
2b.  Body much longer than wide, animal cannot curl into a ball.
                Go to 3

3a.  Body convex above, flat beneath; head with pointed 'beak'.
                Polyzoniida
 
3b.  Body more or less cylindrical, head without 'beak'.
                Go to 4

4a.  Adults with 19 or 20 body segments, no eyes.
                Polydesmida
 
4b.  Adults with more than 20 body segments, usually with eyes.
                Go to 5

5a.  Adults with 30 or 32 body segments, usually with 6 long setae on each tergite.
                Chordeumatida

5b.  Adults with more than 32 body segments, no long setae, body smooth and cylindrical.
                'Juliform' orders: Spirostreptida and Julida