Pelignellus Sturtevant & Wheeler, 1954

Zatwarnicki, Tadeusz & Mathis, Wayne N., 2019, New discoveries in New World Atissini as revealed in revision of Pelignellus Sturtevant & Wheeler (Diptera: Ephydridae), Israel Journal of Entomology (Oxford, England) 49 (2), pp. 11-26 : 15-17

Pelignellus Sturtevant & Wheeler, 1954 (revised status)

Pelignellus : Sturtevant & Wheeler 1954: 252 (type species: Pelignellus subnudus Sturtevant & Wheeler, 1954: 252 , orig. des.); Wirth & Stone 1956: 464 [key], 467 [list]; Wirth 1965: 737 [Nearctic catalog], 1968: 77.6 [Neotropical catalog]; Wirth et al. 1987: 1038–1039 [key]; Mathis & Zatwarnicki 1990 b: 896 [synonymy with Atissa , figures of male terminalia].

Diagnosis: Minute to small shore flies, body length 1.05–1.65 mm; generally densely microtomentose species, especially dorsum of head, thorax, and abdomen.

Head: Frons wider than high; mesofrons weakly to not distinguished from parafrons; 1–2 pairs of interfrontal setae inserted well anterior of anterior ocellus; fronto-orbital setae 3, 2 anterior setae proclinate, inserted anterior of longer, reclinate to lateroreclinate seta; ocellar setae weakly developed, proclinate, shorter than lateral vertical seta; pseudopostocellar setae reduced, mostly lateroclinate but slightly proclinate; lateral vertical seta slighter shorter than medial vertical seta; ocelli arranged in equilateral triangle. Antenna rather short, basal flagellomere as high or higher than long, rounded apically; arista short, not longer than basal flagellomere, bearing 4–5 dorsal rays, these short, length less than width of basal flagellomere. Eye elliptical, bearing numerous interfacetal, fluted setulae, orientation obliquely horizontal. Face in lateral view distinctly concave, excavated, epistomal margin robust, bluntly projected; 2–4 short, pale setae in oblique row ventrolaterally; row of pale, tiny setulae near parafacial. Gena moderately high to high, height greater than height of basal flagellomere. Palpus well developed, yellow.

Thorax: Acrostichal setulae in 2 rows, a prescutellar acrostichal seta well developed; dorsocentral setulae more or less in a single row, only posteriormost seta well developed; 1 prescutellar seta; no postsutural supra-alar setae; scutellar disc with few setulae; 1 lateral and 1 apical seta; notopleural setae 2–3, posterior seta inserted at elevated level from anterior seta, with 1–3 short, pale setulae anterodorsad of anterior seta. Wing generally faintly infuscate, milky gray to faintly tannish; pointed apically near apex of vein R 4+5; crossveins generally infuscate, brown. Abdomen: Tergites uniformly invested with gray to silvery gray microtomentum. Male terminalia ( Figs 3–6, 13–16): Epandrium in posterior view as an inverted U, varying from being parallel sided to being widest at midheight, diamond-like, in lateral view with ventral portion projected anteriorly as a triangle; cercus in posterior view broadly ovate, in lateral view narrowly semihemispherical; surstylus short and robust to elongate and narrow, postgonite in lateral view variable, longer than wide, at last apical half mostly parallel sided, in ventral view elongate, narrow; pregonite small, short, more or less triangular, bearing 2 apical setulae; fused aedeagus/phallapodeme in lateral view elongate, apical half digitiform, basal half more robust and with narrow U-shaped notch or relatively wide concavity sub-basally, in ventral view narrow, moderately elongate, apical third tapered to acutely pointed apex; hypandrium in lateral view very slender, elongate, shallowly sinuous. Female ventral receptacle ( Fig. 10): Operculum bowl-like, with ventral margin flat, extended process J-shaped.

Discussion: According to Sturtevant and Wheeler (1954: 252), Wirth wrote that he had identified two species from Panama. We have carefully studied all specimens available in the USNM, including examination of structures of the male terminalia, and have found that these specimens represent a single species, not two. In addition to the specimens that Wirth collected and observed from Panama, we have since collected large series of the same species from Costa Rica.

In their discussion, Sturtevant and Wheeler further commented about generic assignment, recognizing that although their new species was similar to congeners of Atissa Haliday and Pelignus Cresson (= Schema Becker ), it is also structurally different, which was the main criterion then used for recognition of genera. To broaden their deliberations, they consulted with a noted shore-fly specialist from England, Mr. J. E. Collin, who proffered his opinion, which, according to Sturtevant and Wheeler, suggested that their new species should be treated as an aberrant Atissa , i.e., Collin would expand the generic characterization of Atissa to accommodate this new species. Ultimately, however, Sturtevant and Wheeler (1954: 252) decided otherwise, writing that “While we dislike the multiplication of genera, we cannot agree that this form can reasonably be put in that genus [ Atissa ], nor in any other known to us.”

We have likewise re-examined the question of generic placement, especially as we now have a second species that is closely related and has similar morphologically to P. subnudus . In addition to external characters, we have also studied structures of the male terminalia, and our interpretation is that these structures represent an ancestral state to those found in Atissa . These observations and conclusions are our basis for resurrecting Pelignellus from synonymy with Atissa and placement of these two species in Pelignellus . We hasten to add, however, that our phylogenetic understanding of taxa and lineages within the Atissini is rudimentary, and more comprehensive research and phylogenetic analysis are needed.