The new species is readily separated from other small, variegated Ripipteryx by the elaborately ornamented frons characteristic of Scrofulosa Group species. From other members of the Scrofulosa Group the new species is distinguished by [1] fusion of the superior and inferior frontal folds forming a nasiform median process; [2] the emarginated anterior and posterior margins of the epiproct; [3] the subgenital plate with distinct lateroapical depressions either side of the median line; [4] the strongly bilobed apex of the basal plate of phallus; and [5] the presence of well-demarcated denticular lobes in the dorsal endophallic valves.

Male: Body form small (length 4.54 mm from frons to apex of subgenital plate) and compact with coloration highly variegated (Figs 1–2). Vertex largely black, with crescent-shaped pale cream patches circumscribing the anterodorsal margins of the compound eyes. Interocular distance 0.73 mm. Compound eyes broadly subovoid, 0.86 mm high. Lateral ocelli very small, situated very close to the medial margin of the compound eyes. Median ocellus absent. Frons largely pale cream fringed with reddish brown and bearing numerous elaborate folds and lobes; comprising a central nasiform process formed through fusion of the superior and inferior folds, flanked by deep, sinuous furrows themselves bordered by broad ridges and lobes; frontoclypeal lobe present (Fig. 1). Antennae ten segmented, moniliform, inserted directly beneath the compound eyes. Scape twice as long as pedicel; flagellomeres densely pubescent and wider apically than at their base. Scape, pedicel and flagellomeres 1 and 2 pale cream dorsally and black ventrally; flagellomere 3 almost entirely black; flagellomere 4 with triangular-shaped pale cream patch dorsally and black ventrally; flagellomere 5 almost entirely pale cream; remaining flagellomeres entirely black. Pronotum somewhat tectate anteriorly (Fig. 2), 1.77 mm long, broadly rounded posteriorly; black with broad, pale cream lateral and posterior margins and a prominent orange-brown median patch dorsally that is obovate anteriorly and rhombiform posteriorly. Tegmen entirely black, 2.38 mm long. Hind wing remigium entirely black; posterior fan cream. Profemora 1.18 mm long, black to dark brown dorsally and pale brown to cream ventrally. Protibiae claviform and largely black with a pale cream longitudinal stripe. Mesofemora 1.91 mm long, subquadrate in section, black dorsally and pale cream ventrally. Mesotibiae black with a prominent pale cream longitudinal stripe along the dorsolateral margin. Metafemora large and robust, 3.28 mm long, reddish brown medially with broad pale cream bands dorsally and ventrally; geniculae well-developed, dark reddish brown with pale cream apices. Metatibiae 3.14 mm long, pale yellowish brown with prominent darker dorsal carinae; apical metatibial spurs blade-like with prominent apical hooks, more than twice as long as subapical spurs. Metatarsus sublanceolate, 0.66 mm long, marginally shorter than the apical metatibial spurs. Posterior margin of abdominal tergite 10 broadly emarginate with prominently bilobed membranous median region (Fig. 3). Epiproct with large, densely reticulate lateral lobes and emarginate anterior and posterior margins. Cerci fusiform, bearing numerous long and evenly spaced setae. Paraprocts with large, well-sclerotized and strongly hooked uncuses and robust, apically thickened brachia bearing numerous strong ventroapical setae; brachia only marginally longer than cerci (Fig. 3). Subgenital plate broadly rounded with prominent lateroapical depressions either side of the median line; densely pubescent apically (Fig. 4). Phallus with basal plate strongly bilobed apically; cingulum broad and furcate, thickened laterally and bearing elongate, gently curved apodemes; dorsal valves of the endophallus forming flexible lobes armed with numerous denticles; virga filiform with an uncinate basal articulating process (Fig. 5).

Female: Unknown.

♂: Belize, Toledo District, hand collected on shore of Rio Grande at night, approx. 2 hrs after sunset, 28.1 km NNW of Punta Gorda, 16.31739°N, 88.93442°W, 15 April 2011, sjt11-016, coll. S. J. Taylor, sample # 231, specimen # 0338 (INHS).

The specific epithet honors the Mopan, a Mayan people that live primarily in the southern part of Belize where the new species was collected. There is considerable ethno-historic and toponymic evidence to suggest that the Mopan have lived in this region since before the Spanish conquest (Jones 1998; Wainwright 2009). The Mopan people are recognized by their eponymous language (a form of Yucatec Mayan), spoken by 11, 800 people in Belize and Guatemala (Lewis 2009). The gender of the epithet is feminine.

Ordinarily, we would hesitate to describe a new species based on a single specimen. However, given the number of robust morphological apomorphies there can be no doubt that Ripipteryx mopana is a distinct species. Within the Scrofulosa Group, Ripipteryx mopana is most similar to Ripipteryx biolleyi Saussure, 1896 sharing with this species the loss of the median ocellus and the distinctive nasiform frontal process. The nasiform process in Ripipteryx biolleyi is formed by the upturned apex of the inferior fold strongly overlapping that of the superior fold. Ripipteryx mopana differs in that the apex of the inferior fold is completely fused to the underlying superior fold (Fig. 1). The frontal ornament of Ripipteryx mopana further differs from that of Ripipteryx biolleyi in the presence of carinulated pits on the lateral lobes of the inferior fold and deep, sinuous furrows (rather than ovoid cavities as in Ripipteryx biolleyi) flanking the nasiform process. Both species possess a furcate cingulum with long, slender apodemes, though the apex of the basal plate is strongly bifurcated in Ripipteryx mopana and undivided in Ripipteryx biolleyi. Together, Ripipteryx biolleyi and Ripipteryx mopana appear to be most closely related to Ripipteryx saltator Saussure, 1896 and Ripipteryx saussurei Günther, 1969 sharing with these species a deep invagination of the inferior fold above the frontoclypeal lobe and the development of well-sclerotized denticles in the dorsal valves of the endophallus. These denticles are directed posteriorly and arranged in rows along valvular axial lobes, which are particularly well developed in Ripipteryx mopana (Fig. 5). Denticular lobes are not present in Ripipteryx mediolineata Saussure, 1896, Ripipteryx mexicana Saussure, 1859, Ripipteryx scrofulosa Günther, 1969 and Ripipteryx tricolor Saussure, 1896 all of which instead possess rows of weakly sclerotized, tubercle-like rugosities (Günther 1969). Of these species, Ripipteryx mediolineata and Ripipteryx scrofulosa are apparently the most primitive of the group having the frontal folds poorly developed and lacking a frontoclypeal lobe.