Key to Matthewsius species

1. Pygidium with transverse groove at base narrowed medially (Figs. 3 B, D); elytral striae narrow, shallowly impressed, with simple punctures; elytra glabrous or with extremely fine setae..................................................2

- Pygidium with transverse groove at base not narrowed medially (Figs. 3 A, C, E–F); elytral striae wider, geminate, containing simple punctures, crenulate apically or not; elytra glabrous or with thick setae.....................................3

2. Elytra microreticulate, more evident apically, masking punctures on interstices; striae 7 short, as strongly impressed as 1–6, only present in basal 1/3; eyes separated by about 14 eye-diameters; protibiae without serrations between apical and second tooth; aedeagus with elongate parameres as in Fig. 3 D; northern Queensland..... Matthewsius speewah (Storey & Monteith)

- Elytra shiny, smooth; small punctures on interstices clearly visible; striae 7 much less impressed than 1–6, longer but only present in basal 2/3; eyes separated by more than 20 eye-diameters; protibiae with several serrations between apical and second tooth; aedeagus as in Fig. 3 B; South Australia ........................ Matthewsius penelopae (Matthews & Weir)

3. Clypeal edge with a blunt projection lateral to clypeal teeth; elytral striae punctate but not crenulate; protibiae without serrations between apical and second tooth; aedeagus as in Fig. 3 F; Western Australia ............................................................................................. Matthewsius vanleeuweni Gunter & Weir, new species

- Clypeal edge without a projection lateral to clypeal teeth; elytral striae more-or-less crenulate, at least apically; protibiae with several serrations between apical and second tooth...........................................................4

4. Elytral surface smooth, intervals finely punctate, glabrous; male protibiae abruptly widened apically from second tooth; female pygidium not much more convex than that of male; male metatibiae slightly bent on inner side and slightly twisted; aedeagus as in Fig. 3 A; New South Wales ............................................ Matthewsius illawarrensis (Matthews)

- Elytral surface slightly uneven, intervals with long or short setae; male protibiae gradually widened from base to apex; female pygidium markedly more convex than that of male; male metatibiae slightly bent on inner side but not twisted............5

5. Elytral intervals with punctures bearing long, backwardly curving setae; setae as long as distance between punctures; punctures tending to become elongate laterally; striae deeply impressed; aedeagus as in Fig. 3 C; New South Wales .......................................................................................... Matthewsius rossi (Matthews)

- Elytral intervals with punctures bearing extremely short setae; setae barely longer than the width of a puncture; punctures mainly round laterally; striae less deeply impressed; aedeagus as in Fig. 3 E; New South Wales ................................................................................ Matthewsius stricklandensis Gunter & Weir, new species