Formosargus sagittocerus ( Adisoemarto, 1974 ) Fachin & Hauser, 2022

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, Journal of Natural History 56 (37 - 40), pp. 1513-1562 : 1538-1545

publication ID	https://doi.org/ 10.1080/00222933.2022.2117107
publication LSID	lsid:zoobank.org:pub:A6F9B9FB-D3F9-49F2-8FC1-5E6A5E0AB3B1
DOI	https://doi.org/10.5281/zenodo.7324771
persistent identifier	https://treatment.plazi.org/id/561187CD-FFC3-326B-9B1A-4C39FC4E1770
treatment provided by	Plazi
scientific name	Formosargus sagittocerus ( Adisoemarto, 1974 )
status	comb. nov.

Treatment

Formosargus sagittocerus ( Adisoemarto, 1974) comb. nov.

( Figures 3 View Figure 3 (d), 5(f), 7(d), 8(f–h), 12, 18 (f), 19(a), 24)

Amsaria sagittocera Adisoemarto, 1974: 71 View in CoL (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 View Figure 3 (d)); anterior margin of upper frons with median triangular extension strongly pointing towards antennal insertion ( Figure 5 View Figure 5 (f)). Scutellum mostly dark brown ( Figure 7 View Figure 7 (d)); last three hind tarsomeres brownish ( Figure 19 View Figure 19 (a)).

Material examined

Type material. HOLOTYPE ( Figure 24 View 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 View 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 View 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 View 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 View 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 View Figure 24 ).

Geographic distribution

Oriental Region. Indonesia (West Java) ( Figure 26 View 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 View 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 View Figure 7 (d)) and in the medial area of the upper frons ( Figure 5 View 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 View 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 View 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.