Couplet 29

29a:  Antenna usually longer than one half of body, often inserted on prominence, capable of being reflexed backward over body (Figures 26-73, 26-74); tibia with 2 obvious apical spurs; first antennomere usually several times longer than second; pygidium never sclerotized and exposed; length 3-75 mm in North America.

Cerambycidae  p. 441

29b:  Antenna usually less than half of body, seldom inserted on prominence, not reflexed back over body; tibia with 0-2 apical spurs; length of first antennomere seldom more than 2-3 times length of second; pygidium of some species sclerotized and exposed; length usually <12 mm in North America.