Key to South American genera of Achrysonini (modified and translated from Martins 2002 and Monné & Monné 2004)

1. Setae between ommatidia absent; antennae 12-segmented ................................. Ysachron gen. nov.

– Setae between ommatidia present; antennae 11-segmented ............................................................. 2

2. Sides of prothorax with long spine (longer than pedicel), with curved apex backward ..................... ................................................................................................ Drascalia Fairmaire & Germain, 1864

– Sides of prothorax unarmed (without spines or with small gibbosity) or at most with short triangular tubercle ............................................................................................................................................. 3

3. Pronotum with two tubercles on anterior third; elytra with longitudinal elevation, more evident near base, reaching apical fourth, delimiting a flattened area near suture .. Abyarachryson Martins, 2002

– Pronotum without tubercles (except for small gibbosities in some species of Achryson); elytra uniformly convex or flattened on apical ¾ ....................................................................................... 4

4. Elytra flattened on apical ¾; metafemora linear ..................... Neoachryson Monné & Monné, 2004

– Elytra uniformly convex, metafemora not linear .............................................................................. 5

5. Metafemora strongly clavate ............................................................................................................ 6

– Metafemora subfusiform, with elongate club ................................................................................... 7

6. Antennomere III longer than scape and other antennomeres ...................... Huequenia Cerda, 1890

– Antennomere III shorter than scape and other antennomeres .............. Esseiachryson Martins, 2002

7. Elytra with contrasting punctures and glabrous perimeter ................... Cotyachryson Martins, 2002

– Elytra without contrasting punctures ................................................................................................ 8

8. Basal antennomeres thickened; sides of prothorax with small central gibbosity ............................... .......................................................................................................................... Cerdaia Monné, 2006

– Basal antennomeres linear; sides of prothorax rounded ................................................................... 9

9. Scape about as long or slightly shorter than antennomere III; elytra with long setae and shining aspect ...................................................................................................... Xenocompsa Martins, 1965

– Scape about as long as half the length of antennomere III; elytra often with short setae and general aspect not shining .......................................................................... Achryson Audinet-Serville, 1833