Acerocnema flavifrons Iwasa, 2014

Han, Sangjin & Shin, Seunggwan, 2025, First records of the genus Acerocnema Becker (Diptera: Scathophagidae) from South Korea, with a new species and a newly recorded species using DNA barcodes, Zootaxa 5653 (3), pp. 440-450 : 442-444

Acerocnema flavifrons Iwasa, 2014

( Figs 1C, F, H ; 2E–H )

Acerocnema flavirons Iwasa, 2014: 178 . Type locality: Nakasatsunai , Tokachi, Hokkaido ( Japan).

Diagnosis. This species can be distinguished from congeneric species by the following characters: yellow gena and postgena, well-developed vibrissal angle, black postpedicel, yellow palpus, thorax with microtrichia, scutum with partially large shiny spots between pre- and postsutural dorsocentral and supra-alar lines, yellow legs, male sternite 5 strongly bilobate, very slightly enlarged apically, lobes yellowish white, with whitish setulae over surface but more abundant along inner margin of lobes, and surstylus long and slender not enlarged apically.

Redescription. Male. Face and parafacial yellow; gena and postgena yellow with yellowish white setulae, genal width about one third of vertical diameter of eye. Frontal vitta matt, orangish yellow transitioning to black toward ocellar triangle, pale yellow apically. Fronto-orbital plate and ocellar triangle shiny black; occiput shiny black with yellowish white setulae. Fronto-orbital plate with 3–4 inclinate frontal setae, 3 proclinate orbital setae, 1 pair of proclinate orbital setae, 1 pair of short divergent postocellar setae, 1 long stout inner vertical seta and outer vertical seta absent, as long as postocular setae. Well-developed vibrissal angle with 1 strong vibrissa with 2 short supravibrissal setae and 1 strong subvibrissal setae, all yellow. Antenna with postpedicel black, apically rounded, covered with very fine microtrichia, approximately as long as length of arista; scape and pedicel blackish brown; arista yellow on basal half, black and thinner on apical half, short pubescent apically. Palpus yellow, long, spatulate in ventral view with white hairs over surface; proboscis slender, somewhat stout on basal part, with reduced labella with whitish yellow setulae.

Thorax ( Fig. 1F ). Black with an overall shiny surface, but largely obscured by white microtrichia and all setae yellowish white; scutum covered with white microtrichia and white setulae, partially with two pairs of large shiny spots between pre- and postsutural dorsocentral and supra-alar lines ( Fig. 1H ); acrostichal setae in 2–4 rows, shorter and finer than dorsocentrals; 1–2 presutural and 3 postsutural dorsocentral setae; 2 postpronotal seta; 0 presutural intra-alar setae; 1 presutural supra-alar; 2 notopleural setae; 0 postsutural intra-alar setae; 2 postsutural supra-alar setae; 2 postalar seta; 1 pair of strong basal scutellar setae and 1 pair of convergent strong apical scutellar setae. Anterior margin of presutural dorsocentral lines with 3 erect white setulae. Pleura shiny black, covered with microtrichia except half of dorsal and posterior parts of anepisternum and anepimeron. Proepisternum with 2 whitish yellow proepisternal setae, covered with setulae. Proepimeron with 1 long seta. Anepisternum covered with setulae in posterior half, with 2 long posterior setae. Katepisternum with one strong posterodorsal seta and setulae ventrally. Anepimeron bare.

Wing. Clear, R 1 bare apically on dorsal surface. Calypters whitish with yellowish fine marginal. Halter yellowish.

Legs. Entirely setose. Fore and mid coxae yellow, hind coxae brownish black; femora yellow; tibiae yellow; tarsi yellow, darkened apically from hind tarsomere 3. Setae pale yellow but black on tarsi. Fore femur with dense dorsal hairs. Fore tibia with 1 apical dorsal seta, 1 apical anterodorsal seta, 1 anterodorsal seta on apical 1/2. Mid tibia with 2 anterodorsal setae on apical 1/3 and 2/3, 1 preapical dorsal seta, 1 anteroventral seta on apical 1/3, 1 apical anteroventral seta, 1 apical posterodorsal seta, 1 apical anteroventral seta, 1 apical posterior seta, 1 apical posterodorsal seta. Hind tibia with longer hairs than fore and mid tibiae, difficult to differentiate setae from hairs, with row of 5–6 anterodorsal setae, a row of 6–7 posterodorsal setae, 1 subapical dorsal seta, 1 anterodorsal apical seta.

Abdomen. Shiny black covered with pale setulae over surface. Abdominal sternites shiny black. Sternite 5 strongly bilobate ( Fig. 2E ), rounded and very slightly expanded apically; lobes yellowish white, with whitish setulae over surface, more abundant along inner margin of lobes.

Terminalia ( Fig. 2F–H ). Epandrium shiny black, with long dense setae. Surstylus pale yellow, slender, parallel-sided, not enlarged apically; blackish apically, with setulae and long scattered setae along inner margin, with blackish sclerotized pointy structure on basal part in posterior view. Cercus pale yellow, comprising two sclerotized sections; dorsal section blackish and somewhat parallelogrammatic in posterior view, with long dense stout setae over surface; ventral section long and tweezer-shaped in posterior view, broad in middle and narrower apically in lateral view, with dense setulae from middle to subapical inner surface and black at apex. Pregonite as wide as postgonite in lateral view, severely crooked ventroapically, dense hairs over surface from beginning of bend. Postgonite long and slender, bare and slightly spatulate apically. Epiphallus as slim and long as pregonite. Phallapodeme enlarged, somewhat arched and round ventrally, not digitiform. Hypandrium distinctively arched ventroapically, much thicker and stouter than that of A. saurischia sp. nov.

Material examined (1 ♂). Republic of KOREA: [GW] 1 ♂, Gangwon-do , Yongdae National Recreational Forest , Buk-myeon, Inje-gun, 38°14’27.2”N 128°20’11.5”E, malaise 22.IV–23.III.2023, Han S., Shin S., SNUE02400 ( SNUE) .

Distribution. Republic of Korea (new record), Japan (Hokkaido).

Ecology. Adults have been collected from a flower community of Corydalis ambigua in early spring ( Iwasa 2014).

Remarks. There are inconsistencies in the publication year of A. flavifrons across several papers ( Chagnon & Sinclair 2021; Ozerov 2018; Iwasa 2021; Bernasconi & Šifner 2021), where the year is cited as either 2013 or 2014. Although the original description was intended for publication in 2013, the second issue of Vol. 20 was not printed until 24 September 2014 (stated at the end of the article on page 183). We have confirmed with Dr. M. Iwasa that the actual publication date was 2014. Thus, the correct publication year is 2014, as the actual year of publication takes and therefore, the correct citation is A. flavifrons Iwasa, 2014 .

In the original description, A. flavifrons is noted as having black frontal and orbital setae, as well as black outer vertical setae. However, the examined specimen in this study has yellow frontal and orbital setae and lacks outer vertical setae, in contrast to the original description. Given that both this study and the original description are based on a single male specimen, further specimens are required to assess whether these differences represent intraspecific variation or potential taxonomic significance.

Figures

FIGURE 1. Acerocnema spp., habitus lateral and dorsal views. A–B, D–E, G, Acerocnema saurischia sp. nov., habitus of male (A) and female (B), dorsal view of male (D) and female (E), left half of scutum of male (G); C, F, H, Acerocnema flavifrons, habitus of male (C), dorsal view of male (F), left half of scutum of male (H). Scale bar: 1 mm (A–F). White arrows in (G) indicate partial shiny spots on scutum of Acerocnema spp. Acerocnema saurischia sp. nov. has smaller shiny spots than those of A. flavifrons.

FIGURE 2. Male sternite 5 and terminalia of Acerocnema spp.A–D, A. saurischia sp. nov., male sternite 4 and 5 in ventral view (A); B–C, male genitalia, epandrium, cerci, surstyli in lateral view (B), in posterior view (C), adeagus in lateral view (D). E–H, A. flavifrons, male sternite 5 in ventral view (E); F–G, male genitalia, epandrium, cerci, surstyli in lateral view (F), in posterior view (G), phallus in lateral view (H). Scale bar: 0.25 mm (A, D–E, H); 0.5mm (B–C, F–G). Abbreviations: cerc—cercus; d sec cerc—dorsal section cercus; epiph—epiphallus; pgt—postgonite; ph—phallus; phap—phallapodeme; pregt—pregonite, st—sternite; v sec cerc—ventral section cercus.