Couplet 171

171a:  Ventral appendage of pretarsal claw usually lobe-like, membranous, occasionally bladelike and sclerotized; elytra usually meeting along suture to very near apex, which maybe narrowly and separately rounded; lateral margin of pronotum absent, complete, or indicated only at base; antenna without club, or with vague to distinct club of 3 antennomeres; mid coxal cavities usually narrowly separated, occasionally contiguous; maxillae not forming sucking tube; hind wing with well-developed radial cell; if pronotal margin completely absent, antenna with at least vague indication of club in last 3 antennomeres and mid coxal cavities narrowly separated; if elytra broadly separately rounded, pronotum with lateral carina at base

Stenotrachelidae   p. 438

171b:  Ventral appendage of pretarsal claw bladelike and sclerotized; elytra usually diverging along suture before apex, broadly separately rounded (Figure 26-67A-F); pronotum lacking marginal carina laterally; antenna without club of 3 antennomeres; mid coxal cavities contiguous; maxillae usually normal, sometimes forming a sucking tube; radial cell absent in hind wing; if elytra meeting on suture to very near apex, maxillae modified into sucking tube that extends beyond mandibular apices