Key to species of Lathroeus

1. Pronotum with circular black spots (Figs. 1, 4, 5)............................................................ 2

– Pronotum without circular black spots (Figs. 2, 3, 6, 7, 8)..................................................... 4

2(1). Sides of prothorax with rounded and projected gibbosity (Fig. 1); pronotum with two circular black spots; posterior third of elytra with large, irregular black macula. Unknown place (probably Central or South America)................................................................................................... L. oreoderoides Thomson, 1864

– Sides of prothorax lacking projected gibbosity (Figs. 4, 5); pronotum with four circular black spots; posterior third of elytra lacking large black macula.............................................................................. 3

3(2). Elytral width across humeri smaller than twice elytral length; dorsobasal third of the elytra with one large black circular spot centrally, and another large irregular macula close to humeral carina (Fig. 4). Brazil (Rio de Janeiro, São Paulo, Paraná, Santa Catarina)...................................................................... L. simillimus (Melzer, 1932)

– Elytral width across humeri greater than twice elytral length; dorsobasal third of the elytra with transverse black macula (Fig. 5). Brazil (Minas Gerais, Rio de Janeiro)............................................. L. decoratus (Melzer, 1932)

4(1). Elytra lacking transverse black macula on dorsobasal third (Fig. 3). Brazil (Ceará).............................................................................................. L. immaculatus Nascimento, Bravo & Monné, 2016

– Elytra with transverse black macula on dorsobasal third (Figs. 2, 6, 7, 8).......................................... 5

5(4). Pronotum lacking longitudinal arched black maculae; elytra with large, irregular white pubescent macula distinctly contrasting with remaining surface (Fig. 6). Brazil (Minas Gerais, Espírito Santo, Rio de Janeiro, São Paulo, Paraná, Santa Catarina).................................................................................... L. mysticus Melzer, 1932

– Pronotum with longitudinal arched black maculae (Figs., 2, 7, 8); elytra lacking white pubescence noticeably contrasting with remaining surface......................................................................................

6(5). Scape sinuous; arched black bands on pronotum together inverted U-shaped (Fig. 2). Ecuador, Brazil (Amazonas)..................................................................................... L. interrogationis (Bates, 1863)

– Scape not sinuous; arched black bands on pronotum together not U-shaped (Figs. 7, 8). Brazil (Rio de Janeiro, São Paulo)..................................................................................... L. zikani (Melzer, 1931)