Taxonomy

The previous taxonomic problems with S. rubrithorax were discussed by Maia-Herzog et al. (1984) who designated a neotype for this species. The closest species to S. rubrithorax were considered to be:

• S. bricenoi
• S. conviti
• S. paynei
• S. virgatum s.l.

Taxonomic complications involving S. paynei were discussed in detail and the authors cited S. acatenangoense, S. bilimekae, and S. mathesoni as synonyms of S. paynei and added S. conviti as a new synonym. These synonyms were accepted in the world inventory of the Simuliidae (Crosskey & Howard, 1997, 2004; Adler & Crosskey, 2008, 2009).

Shelley et al. (2002) in a survey of the Simuliidae of Belize provided a comprehensive revision of the closely related S. virgatum and agreed with the synonyms recorded in the world inventory of Crosskey & Howard (1997). The former authors concluded that S. virgatum s.s. from the USA was possibly different to S. virgatum s.l. in which they included specimens from Belize with varying scutal coloration, S. paynei and S. rubrithorax. They suggested future work on S. virgatum s.l. using cytological and molecular techniques to resolve the validity of the constituent species before any firm synonymies could be made.

More recent editions of the world inventory (Crosskey & Howard, 2004; Adler & Crosskey, 2008, 2009) follow Adler et al. (2004) who revalidated S. hippovorum from its synonymy with S. virgatum s.s. These authors also listed the various misidentifications of S. paynei and provided cytological information that suggests that it is a complex of sibling species.

Shelley et al. (2009) re-examined their findings in Shelley et al. (2002) and examined further specimens of S. virgatum s.l.. The authors concluded that the black form from Belize is S. paynei; the brown form from Belize is the same species as S. paynei (Ecuador) and they are possibly conspecific with S. rubrithorax. I re-examined all the latter species in the course of the current work and I agree Shelley et al. (2009)

The S. rubrithorax female is similar in scutal pattern and coloration to S. brachycladum, S. cristalinum and S. lobatoi. but they can be distinguished using other morphological characters [see also Taxonomic Discussion of S. lobatoi].

The gonapophyses of S. rubrithorax are well developed and triangular and less pointed apically than in S. brachycladum and S. cristalinum; the gonapophyses of S. lobatoi are more oval and highly setose.

The ventral extension of the paraproct of S. rubrithorax is sub-oval and membranous and broader with no posterior tails than that of S. brachycladum and S. cristalinum; in S. lobatoi the paraproct is less developed and highly setose.

In the S. rubrithorax male the scutal pattern is most similar to that of S. lobatoi and both are brown. They are distinguished by the ventral plate with no lateral shoulders, median process well developed with median depression, twice as long as the main body of the ventral plate and with a well developed keel with a ventral invagination in S. rubrithorax, whereas in S. lobatoi the ventral plate has small lateral shoulders, a well developed median process extending beyond their apices and with a well developed keel with no invagination, less than half as long as the main body of the ventral plate.

In the pupa S. rubrithorax is easily distinguished from S. brachycladum, S. cristalinum and S. lobatoi by the form and number of the gill filaments.

In Brazil, the larva of S. rubrithorax can be easily distinguished the dissected gill histoblast with eight filaments. The larva of S. paynei, S. bricenoi and S. virgatum s.l. also have a gill histoblast with eight filaments, and they are difficult to separate.

Crosskey & Howard (1997, 2004) placed S. rubrithorax in the PAYNEI species group of the subgenus Hemicnetha, which has been followed by Adler et al. (2004), Coscarón & Coscarón-Arias (2007), and Adler & Crosskey, 2008, 2009). More recently, Shelley et al. (2009) placed S. rubrithorax in the TARSATUM species group within the subgenus Trichodagmia, which is followed in the current work.