Formosargus sagittocerus Fachin & Hauser 2022, comb. nov.
Creators: name: Fachin, Diego Aguilar
name: Hauser, Martin
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Stratiomyidae
Formosargus
Formosargus sagittocerus

description: Formosargus sagittocerus (Adisoemarto, 1974) comb. nov.
(Figures 3 (d), 5(f), 7(d), 8(f–h), 12, 18 (f), 19(a), 24)
Amsaria sagittocera Adisoemarto, 1974: 71 (orig. descr.); 70, figs 1 (head, lateral and dorsal views), 2 (antenna), 3 (thorax, dorsal and lateral views), 4 (fore leg), and 5 (wing).
Type locality: Indonesia, West Java, Tjibodas, Mount Gede. Holotype: ♀ [MZB].
Ref.: Woodley, 2001: 186 (cat.).
Diagnosis
Vertex as broad as ocellar tubercle (Figure 3 (d)); anterior margin of upper frons with median triangular extension strongly pointing towards antennal insertion (Figure 5 (f)). Scutellum mostly dark brown (Figure 7 (d)); last three hind tarsomeres brownish (Figure 19 (a)).
Material examined
Type material. HOLOTYPE (Figure 24 (a–e)), 1 ♀, INDONESIA, West Java, Tjibodas, Mount Gede (MZB). The holotype is without right wing, and fore and hind right legs (except for coxa and trochanter).
Additional material. 1 ♂ (genitalia dissected and stored in microvial with glycerine), INDONESIA, Java [West Java], 15 km NW Bandung, 25 August 1991, Keith Snyder (LACM).
Redescription
Male. Length (n = 1): body, 6.0 mm; wing, 5.5 mm. Head (Figure 3 (d), 5(f)). Vertex area nearly twice shorter than ocellar tubercle size. Upper frons nearly as long as wide, slightly shorter than lower frons; black lateral area of upper frons nearly as broad as ocellar tubercle width, with short yellowish pilosity; anterior margin of upper frons with a median triangular extension strongly pointing towards antennal insertion. Fourth flagellomere dark brown, pointed, as wide as previous flagellomeres combined. Face almost twice shorter than lower frons. Thorax (Figure 7 (d)). Scutum mostly dark, with only a pair of thin brownish anterior lateral lines lateral to medial band and yellow at level of transverse suture; only the medial band extends over transverse suture, reaching apex of scutellum; posterior scutal lateral bands fused to median posterior band, U-shaped; pleuron reddish yellow, with anepisternum and laterotergite marked with dark brown proximally, mediotergite dark brown. Last three hind tarsomeres brownish; mid leg with a hook-like modified structure at base of first tarsomere (Figure 8 (f–h)). Wing. R2+3 originating at r– m level, weakly sinuous towards wing margin. Abdomen. Yellow in background, with a dark brown transverse band over distal half of tergite 1; tergites 2–5 with a pair of subrectangular dark brown spots medially; spots of tergite 3 reduced. Terminalia (Figure 12). Outer margin of genitalia projected; ventral margin of genitalia with a median rectangular plate-like projection; synsternite with a pair of short inner projections, gradually narrowing towards apex, no setae apically. Phallus not exceeding distal margin of gonocoxal apodeme; parameral sheath shorter than gonostylus, wider on distal half. Gonostylus bilobed, much wider on distal half.
Female. Only known from the original description and from the photographs of the holotype provided here (Figure 24).
Geographic distribution
Oriental Region. Indonesia (West Java) (Figure 26).
Comments
In the original description of Formosargus sagittocerus comb. nov., Adisoemarto (1974) mentioned brownish markings at least on the dorsocentral region of the scutum – likely referring to the medial band, on the base of the scutellum, and on the mediotergite. From his illustration (Adisoemarto 1974, p. 70, fig. 3) and holotype images (Figure 24), additional markings, although unclear, can be noted on the anterior and posterior lateral margins of the scutum, that may indicate a similar colour pattern to that seen in the male here presented. The LACM male is indeed darker than the female in the scutum (Figure 7 (d)) and in the medial area of the upper frons (Figure 5 (f)) as well. However, some level of sexual dimorphism is observed in the genus regarding the colour intensity of the body, in which the females are usually lighter than males in the head and thorax, often with smaller dark markings, but darker, with broader markings, in the abdomen (see Figure 20 (b and d) for comparison). The record of the male, again in Indonesia (West Java), less than 100 km west of the collection site of the female holotype (Figure 26), is additional evidence to sustain this specimen in the species.
It is worth noting that the antenna of the holotype of F. sagittocerus illustrated by Adisoemarto (1974, p. 70, fig. 2) shows seven flagellomeres, but it probably has five, as in nearly all Sarginae. The conical shape of the flagellum in the illustration is the result of an enlargement of the fourth flagellomere in both sexes of some species of Formosargus. This also is present in F. trivittatus sp. nov., F. variegatus and F. woodleyi sp. nov.
description: Published as part of Fachin, Diego Aguilar & Hauser, Martin, 2022, Revision of Formosargus James, 1939 (Diptera: Stratiomyidae): five new species in an otherwise rare genus and Amsaria Adisoemarto, 1974 as a generic synonym, pp. 1513-1562 in Journal of Natural History 56 (37 - 40) on pages 1538-1545, DOI: 10.1080/00222933.2022.2117107, http://zenodo.org/record/7318178