Cabamofa vietnamensis Jaschhof & Levesque-Beaudin, 2022

Jaschhof, Mathias, Levesque-Beaudin, Valerie, Broadley, Adam, Heller, Kai, Lien, Vu Van & Schmidt, Stefan, 2022, Description of Cabamofa vietnamensis sp. nov., the second species of Cabamofa in mainland southeast Asia (Diptera: Bibionomorpha: Sciaroidea incertae sedis), Zootaxa 5182 (3), pp. 297-300 : 297-298

Cabamofa vietnamensis Jaschhof & Levesque-Beaudin sp. nov.

( Figs 1–4 )

Diagnosis. The new species, which is largely similar to C. orientalis , is distinguished mainly by genitalic characters, as follows ( Fig. 4 versus Jaschhof & Ševčík 2019: fig. 5). Of the gonostylus, the apex is narrower, lacking the angulate outgrowth found in C. orientalis , and the inside bears 2 conspicuously large setae (in Sciaroidea usually referred to as megasetae, arrow-marked in Fig. 4 ) as opposed to 5 slightly smaller setae found in approximately the same positions in C. orientalis . The tegmen is considerably broader and the area of fine aedeagal teeth at the posterior tegminal edge is markedly smaller. The anterior edge of the gonocoxal synsclerite is evenly rounded, not truncate as in C. orientalis . Finally, the ninth tergite is longer, and its maximum width is found in the anterior third, not at about the midlength as in C. orientalis . Other, minor distinctions concern the wing ( Figs 2‒3 versus Jaschhof & Ševčík 2019: figs 2 and 4): in C. vietnamensis, Rs is situated at about the same level as the base of M 4 (not clearly basally of it); R 1 is slightly longer, joining the costa beyond (not before) the midpoint of wing; and the U-shape formed by M 1+2 is slightly shorter. See also the remarks on identification given below.

Other male characters. Body length 2.8 mm. Head. Clypeus non-setose. Scape slightly larger than pedicel, both setose, lighter in color than flagellum. Fourth flagellomere elongate-cylindrical, with short neck, node 2.5 times as long as wide, with irregular cover of fine setae whose lengths equal the flagellomeral width, interspersed with a few larger setae arising from sockets (similar to C. orientalis, Jaschhof & Ševčík 2019 : fig. 1). Compound eyes touching at vertex, eye bridge 7‒8 ommatidia long. Palpus with 5 setae-bearing segments, third segment conspicuously swollen, with sensory pit, fifth segment conspicuously long and thin (similar to C. orientalis, Jaschhof & Ševčík 2019 : fig. 3). Legs. Coxal lengths relative to thoracal height: forecoxa, 0.75, midcoxa, 0.60, hindcoxa, 0.50. Edge of foretibial anteroapical depression with comb of about 15 straight, stiff setae. Apices of mid- and hind tibia with comb of 8 and 12 setae, respectively, similar to those on foretibia but more widely spaced. Claws small, strong, crescent-shaped, toothless. Empodia small, barely claw-long. Wing ( Figs 2‒3 ). As long as body, 2.3 times as long as wide. Veins clearly contoured except for Rs which is decidedly pale. Abdomen. Segments 1‒6 normal size, tergite and sternite of a particular segment ending on same level; segment 7 considerably shorter than anterior segments, sternite twice as long as tergite; segment 8 similar to 7 but still shorter. Genitalia ( Fig. 4 ). Ninth tergite with setae of various lengths, posterior edge with several large setae pointing inwards (ventrad). Gonocoxal synsclerite with wide, shallow emargination medioposteriorly, below the emargination a more poorly sclerotized, non-setose portion that extends almost to the anterior gonocoxal edge; lateral setae larger than medial setae; dorsal apodemes slender, slightly longer than the distance separating them. Gonostylus with narrow, stemlike base; apical portion broadened into medial lobe of considerable size, covered in numerous thick setae of various lengths, head of lobe with small, blunt-ending, sclerotized tooth largely hidden among the setae. Parameres merged to form a subrectangular, weakly sclerotized plate (tegmen) with convex, weakly contoured posterior edge, lateral edges reinforced by sclerotization. A small, inconspicuous area of fine aedeagal teeth medially at tegminal edge. Ejaculatory apodeme about as long as tegmen, well sclerotized, very slightly broadened towards apex. Cerci small, halfmoon-shaped, setose. Hypoproct conical, non-setose, densely microtrichose.

Female and preimaginal stages are unknown.

Molecular identification. The COI sequence (651bp) is available on BOLD (http://boldsystems.org/): BIN BOLD: AEJ2606, dataset (dx.doi.org/10.5883/DS-CABAMOFA); and on GenBank (accession: OK502254 ).

Etymology. The name refers to the geographical distribution of the new species in Vietnam.

Type material. Holotype (used for DNA extraction, body partly dissected and mounted on microscope slide in Canada balsam): male, Vietnam, Ninh Binh province, Cuc Phuong National Park , near Park Centre, 400 m elevation, 20.351°N: 105.594°E, 29.ix.2019, Malaise trap, V.V. Lien (specimen VNMN.IS.CP.00001 in Vietnam National Museum of Nature, Hanoi).

Remarks on identification. Morphology. In terms of size and habitus, species of Cabamofa can be mistaken for Sciaridae , which usually are plentiful in Malaise trap samples. An eye-catching peculiarity of Cabamofa concerns the wing: since the anterior branch of the medial vein (M 1+2) lacks the basal (stem) portion, the apical portion (furca) is isolated and forms a perfect U-shape near the wing apex ( Figs 1‒2 ). Also, fresh male specimens of C. vietnamensis in ethanol show a yellowish thorax that is in contrast with the dark-brown abdomen, the fairly large genitalia being lighter again; the resulting dichromatism differs from the plain-colored black or brown exhibited in most Sciaridae . These two features in combination should raise attention when visually examining sciaroids using a dissecting microscope. To identify Cabamofa to species, the genitalic structures of males ( Fig. 4 ) need to be investigated by transmitted-light microscope.

DNA barcoding. The specimen was sequenced for COI. When blasted against the BOLD ID engine, the nearest neighbors (as of early March 2022) were from 13.33% to 14.01% distant and matched a wide range of families: Agromyzidae , Empididae , Limoniidae and Mycetophilidae . When blasted against GenBank, the closest matches were from 13.71% to 14.29% distant and matched again a wide range of families: Culicidae , Empididae , Mycetophilidae and Phoridae . As other unplaced genera from Sciaroidea incertae sedis are present on both sequence databases and none are in the top matches, it shows how widely divergent Cabamofa really is. While we regard this finding as irrelevant for the actual systematic position of Cabomofa within the Sciaroidea, it shows the imperative necessity to perfect the global DNA barcode reference library. For insects, as rarely encountered as most Sciaroidea incertae sedis are, it is a hugely challenging task. At this time, it would be almost impossible to correctly identify Cabamofa specimens based on COI or discover new species without morphology.

Figures

FIGURES 1–4. Cabamofa vietnamensis sp. nov., male holotype. 1: Habitus, lateral (specimen in ethanol after DNA extraction). 2: Wing, dorsal, setae omitted. 3: Base of wing, dorsal, setae omitted. 4: Genitalia, ventral. Scale for 1 and 2, 1.0 mm, for 3, 0.5 mm, and for 4, 0.1 mm. Abbreviations: cerc = cercus, hyp = hypoproct, tgm = tegmen, tg9 = ninth tergite.