Genus Oecleus Stål, 1862: 306.

Type species Oecleus seminiger Stål, 1862: 307.

Diagnostic summary (modified from Kramer 1977). Small to midsize (3.3–8.5 mm); head narrower than pronotum (in dorsal view) with eyes large. Vertex narrow, trough-like and parallel-sided, lateral and anterior margin carinate. Slightly raised; proximally narrowed and distally produced beyond eyes for a variable distance. In lateral view, apex of head acutely or obtusely angled, eyes emarginate, ocellus present under each eye and near midline above frontoclypeal suture. In frontal view, frons elongated and narrowed toward vertex, carina on midline of frons present (sometimes obsolete). Clypeus triangular or subtriangular. Antennae originating from large socket, scape reduced and collar-like, pedicel rounded with sensoria, flagellum beadlike basally and filamentous distally. Pronotum collar-like with irregular ridges, narrowest on midline, indented on posterior margin, carinate on posterior and lateral margins. Mesonotum longer at midline than combined lengths of vertex and pronotum, mesonotum flattened, usually bearing five longitudinal carinae, sometimes carinae flanking central carina absent or reduced to pigmented lines. Hind tibiae without lateral spines. Forewings clear, rarely with color pattern, veins usually dotted with dark pustules, often bearing setae. Male terminalia with pygofer longest on ventral margin, anal tube elongated, paired slender symmetrical gonostyli (‘styles’ of Kramer 1977) flanking median lobe of pygofer; gonostyli and basal portion of asymmetrical aedeagus articulated by vertical connective. Aedeagus consisting of a ridged basal phallotheca (periandrium, “shaft” of Kramer 1977) and distal, movable retrorse flagellum (endosoma); phallotheca with 1 to 3 processes, flagellum with 0 to 2 processes.

Remarks. Oecleus is distinctive and can be separated from all other Cixiidae in our fauna by characters of the head in dorsal view. The vertex, is greatly narrowed and trough-like, mainly parallel sided but narrower proximally than apically and is separated from the front by a short transverse carina. These features separate Oecleus from all genera in Oecleini except possibly Rhamphixius, which (e.g.) has a greatly projected vertex, and possibly Antillixius. Antillixius, known only from Cuba, which has a sharply pointed head (in lateral view), vertex very deeply trough-like, with the lips of the trough contiguous all the way between the eyes, 3 carinae on the mesonotum, veins of wings without granulations (Myers 1928). Nymphocixia and Nymphomyndus have the vertex narrow, but the head appears broadly rounded from lateral view.