Key to genera related to Phthia

1 Metathoracic peritreme bilobate (Fig. 16); clavus and corium rather dull or scattered with metallic iridescence. ....................................................................................................... 2

– Metathoracic peritreme undivided, not bilobate (Fig. 17); clavus and corium entirely with metallic green iridescence. ........................................................... Phthiadema gen. nov.

2 Body surface entirely rather dull; humeral angles truncate, not exposed (Fig. 19). ......... .................................................................................................... Phthiacnemia gen. nov.

– Body surface scattered with metallic iridescence; humeral angles acute to subacute (Figs. 1, 4). ................................................................................................................................ 3

3 Posttylar depression absent; hind femora dorsally tuberculate; humeral angles remarkably expanded into large and acute spine directed outward and forward (Fig. 4); calli with two conspicuous projections (less developed in females) each lateral to midline. .................. .................................................................................................... Rhytidophthia gen. nov.

– Posttylar depression forming single sulcus; hind femora dorsally smooth; humeral angles tapering into short or medium size acute to subacute spine, directed outward and never forward (Fig. 1, 5); calli without spine projections. ....................................................... 4

4 Dorsal surface of head entirely metallic green; anterolateral borders of pronotum dentate; posterior lobe of pronotal disk without longitudinal medial carinae; abdominal sterna III–VI lateral to midline without yellowish to reddish orange maculae. .......................... ........................................................................................................ Phthiarella gen. nov.

– Dorsal surface of head entirely rather dull; anterolateral borders of pronotum smooth; posterior lobe of pronotal disk with low longitudinal carinae; abdominal sterna III–VI lateral to midline with rectangular yellowish to reddish orange maculae. ........................ ............................................................................................................... Phthia Stål, 1862