Couplet 76

76a:  Antenna with 7-9 antennomeres, antennomeres 7-9 usually forming a loose, tomentose club, antennomere 6 often forming a cupule at base if club; maxillary palps often as long or longer than antenna (Figure 26-22), always longer than half antenna length; hind coxa with ventroposterior carina setting off posterior face that rotates against anterior excavation of first ventrite; planes of ventral surface of hind coxa and first ventrite discontinuous; hind trochanter inserted on ventral (not posterior) surface of coxa (Figure 26-22B), femur held against ventral face of coxa, not against posterior face of coxa, or flat to abdominal surface when fully retracted

Hydrophilidae   p.406

76b:  Antenna variable but not as in preceding entry; maxillary palp usually much shorter than antenna, hind coxa configured differently