Body bicoloured, head light brown medially but paler at anterior and posterior areas; pronotum, mesonotum and metanotum brown; abdominal tergites II–V brown at least laterally, VI yellow, VII–IX dark brown, X yellow; fore wing with 2 pale bands, apex dark, clavus dark with pale setae; antennal segments I–III pale, apex of IV –V light brown; hind tibiae yellow, femora shaded with light brown. Head with occipital apodeme confluent with posterior margin of eyes, ocellar area striate with markings between the striae; antennal segments III & IV with apex not forming an elongate neck. Pronotum transversely striate with many markings between the striae; mesonotum and metanotum striate with markings between the striae; metasternal plate with shallow emargination. Fore wing second vein with one seta distally. Abdominal tergites VII–VIII with complete comb of microtrichia on posterior margin, but this is shorter on VII, also VI sometimes with very short comb medially and no comb on remaining tergites; tergite IX with 2 pairs of mid-dorsal setae; sternites without microtrichia medially, or with one row.
Male similar to female but smaller, sternite VII with very small circular pore plate.
Intraspecific variation
Specimens collected from Santa Catarina are paler than the specimens from the type series.
Genus and similar species information
Almost 120 species are included in Neohydatothrips, most from tropical countries (Mound & Tree 2009). All of them have the abdominal sternites and lateral thirds of tergites covered by rows of fine microtrichia, with many of them being bicoloured and with banded fore wings. Although generally similar to N. portoricensis, the pronotal sculpture of N. ruginosus is more delicate, and the metanotal sculpture more complex. A key to the Neotropical species of Neohydatothrips is provided by Lima & Mound (2016).
