Stichillus Enderlein 1924

Genus Stichillus Enderlein, 1924

Stichillus Enderlein, 1924: 279. Type species: Stichillus acutivertex Enderlein, 1924 (= Hypocera insperata Brues, 1911) (by original designation).

Tressinus Schmitz, 1924: 149. Type species: Hypocera johnsoni Brues, 1904 (by original designation).

Tristichothyrsus Enderlein, 1936: 118 (nomen nudum).

Diagnosis for genus (modified from Brown 1992; Nakayama & Shima 2004). Frons without supra-antennal setae. Vertex flat, with posterior margin curved upwardly forming distinct transverse ridge; ocellar region demarcated by sinuated line forming three loops; lateral ocelli widely separated, situated close to eye margins. Male first flagellomere oval or pyriform (globose in female). Anepisternum with short setae on upper part. Hind tibia with 2–3 dorsal longitudinal setal palisades. Wing with vein R 2+3 absent. Male hypopygium nearly symmetrical; hypandrium with semi-triangular membranous lobe on each ventrolateral side, spinulose; aedeagus generally tubular, composed of dorsal shoe-like plate and ventrally extended membrane.

Remarks. The three-looped demarcated ocellar region is a synapomorphy of the Stichillus species and has been used traditionally in species identification. Many species, however, have very similar characteristics in ocellar regions that are indistinguishable from one another (e.g., S. japonicus and S. koreanus sp. nov., as in Fig. 2C–F). Furthermore, the shape of the ocellar region shows some degree of intraspecific variation in same sex (Fig. 3), as well as in between sexes (Fig. 2E, F). Although the unusual types of ocellar region of some species can be a good diagnostic character for the species (e.g., the Chinese species S. suspectus (Brues) and S. tuberculosus Liu & Chou, see Liu 2001: figs. 68, 74), the usefulness of shape of ocellar region in species identification is in doubt due to high degree of intraspecific variation and interspecific similarity.