Pachybrachis stygicus, Fall, 1915

Barney, Robert J., 2019, Key to All Sixty-Four Species of Pachybrachis Chevrolat (Coleoptera: Chrysomelidae: Cryptocephalinae) in the Eastern USA, The Coleopterists Bulletin 73 (1), pp. 85-96 : 90

54. Median lobe with median orificial plate large and heavily sclerotized, conspicuous, shaped like an inverted ladle ............................. ................... 55. P. stygicus Fall (in part)

54 ʹ. Median lobe not as above ................... 55

55. Subplanar surface of median lobe with paired apico-marginal denticles or pointed protuberances ....................................... 56

55 ʹ. Subplanar surface of median lobe without paired apico-marginal denticles or pointed protuberances ................................... 66

56. POL of median lobe arrowhead-shaped when viewed from above, with ALA deflexed 90° from vertical at ALM ........................ 57

56 ʹ. POL of median lobe with ALA deflexed 80° at ALM .......................................... 62