Palaeosepsioides mitarakensis Silva, 2020

Silva, Vera C. & Pollet, Marc, 2020, The Sepsidae of the Mitaraka expedition, French Guiana (Diptera), Zoosystema 42 (14), pp. 195-205 : 201-202

Palaeosepsioides mitarakensis Silva , n. sp.

( Fig. 2 )

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TYPE MATERIAL. — Holotype. French Guiana • ♂; Mitaraka , MIT- A-RBF1; 02°14’11.4”N, 54°27’07.0”W; 306 m a.s.l.; on vegetation along muddy trail and in swamp; 6.III.2015, sweep net, Marc Pollet leg.; FR-GU/ Mitaraka /2015; sample code: MITARAKA/074 (sorted by Marc Pollet, 2015); MNHN.

DIAGNOSIS. — This species is distinguished by a hyaline, spotless wing, the abdominal sternite 4 without long apical lateral lobes, and the male fore femur with two short and strong setae near middle.

ETYMOLOGY. — Named after the type locality of the species, i.e., the Mitaraka Mountains in the southwest of French Guiana.

DESCRIPTION

Male

Measurements. Length of body 2.1 mm. Length of wing 2.3 mm.

Color. Frons blackish brown in posterior third and yellowish brown in anterior two thirds; face and gena whitish yellow. Postcranium with occiput blackish brown and postgena yellowish brown; thorax and abdomen brownish yellow, medial postsutural scutum posterior to the anterior dorso-central seta and scutellum brownish. Legs yellow in the following parts: all coxae, anterior part of fore femur, fore tibia, apical two thirds of mid tibia, and all tarsi. Mid and hind femora brown, with basal part yellowish. Basal third of mid and hind tibiae blackish brown, and apical third of hind tibia brown. Wing without dark spot near apex. Basal costal cell, membrane area posterior to stem vein completely, and costal cell in basal half, blackish.

Pruinescence. Frons shiny. Face and gena subshiny. Postcranium thinly greyish pruinose, shiny only along eye. Scutum slightly golden pruinose. Proepisternum (except for greyish pruinose ventral margin), anepisternum and anepimeron shiny. Katepisternum shiny, but with a large greyish pruinose dorsal stripe. Proepimeron, katepimeron, meron and metepisternum thinly greyish pruinose. Metepimeron shiny. Katatergite and anatergite greyish pruinose. Mediotergite shiny. Scutellum greyish pruinose. Abdomen shiny.

Head ( Fig. 2B ). Somewhat flattened dorsoventrally; eye round. First flagellomere elongate ovoid in lateral view, approximately 1.5 times as long as wide, blunt apically. Arista bare. Chaetotaxy: ocellar setae long, postocellar setae lateroclinate, inner and outer vertical setae present; fronto-orbital seta absent; one pair of vibrissae present; occipital sclerite with several setulae; postgena without a seta near lower margin.

Thorax ( Fig. 2A, C ). Postpronotal lobe and scutum with scattered setulae. Chaetotaxy: one postpronotal, two notopleural, and one supra-alar setae, postalar seta absent, and dorsocentral setae arranged 0+ 2. Anepisternum in posterior half with scattered setulae and with a long seta near posterior margin. Scutellum with well-developed apical setae; basal setae short. Postmetacoxal bridge absent (metapleura separated from each other).

Legs ( Fig. 2A, D ). Fore coxa long and simple, with one dorsal seta apically. Fore femur and tibia as in Fig. 2D . Mid coxa with a row of setulae in upper half. Mid femur with two strong anterior setae in center. Mid tibia with one strong ventral, one preapical anterodorsal, one apical posteroventral and one anteroventral setae. Hind femur without major setae. Hind tibia without osmeterium, and with one apicodorsal seta.

Wing ( Fig. 2E ). Hyaline, with only basal costal cell, costal cell and base of wing dark brown. Basal medial and basal radial cells separate. Anal vein long. Alula entirely covered with microtrichia, narrow. Upper calypter with setulae on margin. Halter white.

Abdomen ( Fig. 2A ). Strongly constricted after syntergite 1 + 2. Tergites 2-5 each with longer marginal setae. Apical margins of sternites 3 and 4 with longer setae; sternite 4 not modified ( Fig. 2F ).

Female

Unknown.

NOTE

The abdomen of the holotype was not dissected because the male specimen is unique, and the species is adequately defined by external characters. As the abdomen was not bended under the body it was possible to identify some of the features (see further).

REMARKS

Based on the current knowledge of Neotropical sepsids, and using the key of Silva (2010), this male specimen collected in the Mitaraka survey keyed out to Palaeosepsioides Ozerov, 1992 . It did not match, though, two of the characters of the generic concept as defined by Ozerov (1992): “absence of hairs on the upper calypter margin” (the specimen shows long setulae on the upper calypter margin) and “the abdominal sternite 4 extremely long, with long lateral lobes, considerably longer than abdominal sternite 5” (our specimen shows only long setae on the posterior margin of tergite 4). However, its abdomen features a strong constriction after tergite 1 + 2 and lacks a postmetacoxal bridge. It certainly does not belong to Meropliosepsis Duda, 1926 , Meroplius Rondani, 1874 or Themira Robineau-Desvoidy, 1830 due to the absence of a well-developed fronto-orbital seta; nor can it be assigned to Microsepsis Silva, 1993 as the male terminalia are symmetrical and the CuA + CuP vein is longer than the length of the cell cua. It does not belong to Archisepsis Silva, 1993 or Pseudopalaeosepsis Ozerov, 1992 either because it shows an elevation in the posterior margin of the syntergite 1 + 2 and the abdominal tergites are polished and shiny, with short setae. And finally, it does not fit into Lateosepsis Ozerov, 2004 nor Palaeosepsis Duda, 1926 because it does not have a postmetacoxal bridge. As a result, it seems most appropriate to assign it to Palaeosepsioides and to adjust the definition of the genus in anticipation of more material to be collected in order to carry out a phylogenetic analysis of the sepsid genera that include this taxon.

Figures

FIG. 2. — Palaeosepsioides mitarakensis Silva, n. sp., male holotype: A, habitus, lateral view; B, head, lateral view; C, habitus, dorsal view; D, left fore leg, posterior view; E, wing; F, posterior part of abdomen, ventral view. Scale bars: 0,5 mm, except Fig. 2A, 2,5 mm.