New species and records of the subgenus Libnotes (Laosa) Edwards (Diptera, Limoniidae) from China with a key to world species

Abstract Twenty species of Libnotes (Laosa) Edwards, 1926 are known worldwide and three are known from China so far. Here, two species of Laosa are added to the Chinese fauna, of which L. (L.) baiyunensissp. nov. is described and illustrated as new to science, and L. (L.) fuscinervis Brunetti, 1912 is newly recorded from China. Morphologically, the new species is most similar to L. (L.) charmosyne (Alexander, 1958) but can be distinguished by the pleura of the thorax, the relative position of the additional cross veins in cell r3 and r5, and the details of the male genitalia. A key to the world species of Laosa is presented.


Introduction
Libnotes Westwood, 1876 is a species-rich Limoniidae genus with a total number of 293 species and subspecies, separated into eight subgenera: Afrolimonia Alexander, 1965, Goniodineura van der Wulp, 1895, Gressittomyia Alexander, 1936a, Laosa Edwards, 1926, Metalibnotes Alexander, 1972, Neolibnotes Alexander, 1972and Paralibnotes Alexander, 1972. The subgenus Laosa constitutes a small group within the genus with 20 known species from the Oriental (nine species), Australasian/ Oceanian (eight species) and Palaearctic (three species) regions (Oosterbroek 2021), and here an additional new species from China is described and illustrated. It can be easily distinguished from other subgenera by the wing having two additional cross veins in cells r 3 (r-r) and r 5 (r-m, absent in some species) and Sc 1 ending far beyond the fork of Rs. Detailed features for recognition were given by Edwards (1926) and Podenas and Byun (2018).
Three species of the subgenus Laosa were previously recorded from China: L. (L.) diphragma (Alexander, 1934a), L. (L.) regalis Edwards, 1916 and L. (L.) transversalis de Meijere, 1916. In this paper, two Laosa species are added to the Chinese fauna, of which L. (L.) baiyunensis sp. nov. is described and illustrated as new to science and L. (L.) fuscinervis Brunetti, 1912, known previously only from India, is newly recorded from China. A key to the world species of Laosa based on types and non-type specimens, and on the literature is presented.

Material and methods
Specimens for this study were collected from several localities in China by different entomologists between 2002-2016. Type specimens are deposited in the Entomological Museum of China Agricultural University, Beijing, China (CAU). Other studied specimens are deposited in Qingdao Agricultural University, Shandong, China (QAU). We also examined specimens from the National Museum of Natural History, Smithsonian Institution, Washington D.C., USA (USNM) and the Natural History Museum, London, UK (NHM) ( Table 1). Genitalic preparations of males were made by macerating the apical portion of the abdomen in cold 10% NaOH for 12-15 hours. Observations and illustrations were made using a ZEISS Stemi 2000-C stereomicroscope. Photographs were taken with a Canon EOS 77D digital camera through a macro lens. Details of coloration were examined in specimens immersed in 75% C 2 H 5 OH. Table 1. Information of the examined specimens from USNM and NHM.

Taxonomy
Key to world species of Laosa Basal 1/4 of wing with complete or broken crossband; m-m shorter than basal section of M 3 (Fig. 1a- Rs nearly straight or slightly curved, r-r far beyond r-m and distance between them more than twice length of r-r (Fig. 1c)  Diagnosis. Anterior scutum brown with side edges brownish black. Pleura brownish yellow with a broad brownish black stripe extending from cervical region to base of wing. Tip of wing round. Wing nearly unpatterned except some pale brown patches around cross veins and portions of longitudinal veins, without conspicuous crossband from top to bottom. Sc long, ending near middle of cell dm. Rs slightly curved. R 2 slightly before tip of Sc 2 . Two additional cross veins in cells r 3 and r 5 , the former (r-r) beyond distal end of cell dm, the latter (r-m) aligned with distal end of cell dm; m-m twice as long as basal section of M 3 . Basal section of CuA 1 far beyond fork of M and at about 1/3 of cell dm. Tip of A 2 nearly straight.
Description. Male. Body length 12.0-14.0 mm, wing length 19.0-22.0 mm. Head (Fig. 2b). Brown. Hairs on head brown. Antenna length 2.9 mm, brown. Scape long cylindrical; pedicel oval, nearly as long as first flagellomere; flagellomeres oval, tapering apically, terminal flagellomere 1.5 times as long as preceding segment. Mouthparts brown with white hairs; palpus brown with brown hairs. Thorax (Fig. 2c). Pronotum brown with sides brownish black. Prescutum brown with side edges brownish black. Anterior scutum brown with side edges brownish black; posterior scutum brown. Scutellum pale brown. Mediotergite pale brown with sides brownish black. Pleura (Fig. 2a) brownish yellow with a broad brownish black stripe extending from cervical region to base of wing. Hairs on thorax white. Coxae yellow; trochanters pale yellow; femora yellow to brownish yellow with tips dark brown; tibiae brown; tarsi brown. Hairs on legs dark brown. Wing (Fig. 2d) tinged with pale brownish yellow. Darkened areas around cross veins, distal end of cell dm and CuA 1 , tip of M 1+2 , CuA and A 2 ; three small spots at base of Rs, at fork of Sc, and over R 2 and tip of Sc 2 . Venation: Sc long, ending far beyond fork of Rs and near middle of cell dm. Basal section of Sc 2 very close to tip of Sc 1 . Tip of Sc 2 nearly transverse, indistinct at wing margin. Rs very short, slightly sinuous. R 2 slightly before tip of Sc 2 . Radial and medial veins distinctly curved caudally before wing margin. Two additional cross veins in cells r 3 and r 5 , the former (r-r) at middle of cell r 3 , the latter (r-m) at basal 2/5 of cell r 5 and aligned with distal end of cell dm. Cell dm elongate, more than 5 times as long as its width; m-m elongate, twice as long as basal section of M 3 . Basal section of CuA 1 far beyond fork of M and at about 1/3 of cell dm. A 1 straight. A 2 slightly sinuous. Halter length 2.6 mm, yellow with knob brown.
Abdomen. Tergites brownish yellow with a brown median stripe, lateral borders brown; eighth tergite brown. Sternites brownish yellow with eighth sternite brown. Hairs on abdomen white. Hypopygium (Fig. 3). Ninth tergite with widely rounded posterior margin and small median emargination. Gonocoxite elongate, slender with an elongate, bluntapexed ventromesal lobe; inside edge with small setose bulge. Outer gonostylus arched at 2/3 length, tip acute. Inner gonostylus short, oval with long, arched rostral prolongation armed with two spines near base from a single tubercle; an elongate lobe arising dorsally near base with a brush of long setae at apex, at right angle to lobe and directed laterally. Paramere wide at base, elongate, triangular distally. Penis long, tip sunken in the middle.
Female. Body length 11.5 mm, wing length 17.5 mm. Similar to male, but eighth tergite brownish yellow with a broad brown median stripe. Tenth tergite brown. Cercus (Fig. 2e) brown, tip slightly exceeding tip of hypogynial valve. Hypogynial valve brownish yellow with borders darker, base slightly beyond base of tenth tergite.
Etymology. The species is named after the type locality Mt. Baiyun.

Distribution. China (Henan).
Remarks. This species is somewhat similar to L. (L.) charmosyne from South Korea and Japan in having similar spots on the wing, but it can be easily distinguished from the latter by the pleura of the thorax being brownish yellow with a broad brownish black stripe, the crossvein r-r being 1.5 to 2 times its length before R 2 , the crossvein r-m being aligned with the distal end of cell dm, the basal section of CuA 1 being far beyond the fork of M and at about 1/3 of cell dm (Fig. 2d), and the inner gonostylus being about 2/3 length of the gonocoxite (Fig. 3a), whereas in L. (L.) charmosyne, the pleura of the thorax is dark brownish gray, the crossvein r-r is near R 2 , the crossvein r-m is distinctly before the distal end of cell dm, the basal section of CuA 1 is beyond the fork of M and at 1/6-1/5 of cell dm, and the inner gonostylus is half the length of the gonocoxite (Alexander 1958;Podenas and Byun 2018). Brunetti, 1912 Figs 4-5 Libnotes fuscinervis Brunetti, 1912: 411. Type locality: Dajiling, East Himalayas (India). Diagnosis. Anterior scutum brown with a broad, posteriorly subdivided, dark brown median stripe and a spot on each side of it; posterior half of median stripe with a paler division that broadens out across posterior scutum and scutellum. Pleura brownish yellow with a broad, anteriorly indistinct, brownish black stripe extending from cervical region to mediotergite. Tip of wing round. Wing with many conspicuous spots but without conspicuous crossband from top to bottom. Sc long, ending at 1/3 of cell dm. Rs slightly curved. R 2 before tip of Sc 2 and distance between them about length of R 2 . Crossvein r-r before distal end of cell dm. Additional cross vein in cell r 5 absent; m-m twice as long as basal section of M 3 . Basal section of CuA 1 far beyond fork of M and at about 1/4 of cell dm. Tip of A 2 slightly curved.

Libnotes (Laosa) fuscinervis
Description. Male. Body length 9.5 mm, wing length 14.5 mm. Head (Fig. 4b). Brownish yellow. Hairs on head brown. Antenna length 2.0 mm, dark brownish yellow. Scape long cylindrical; pedicel oval, nearly as long as first flagellomere; flagellomeres oval, tapering apically, terminal flagellomere 1.5 times as long as preceding segment. Mouthparts brown with white hairs; palpus brown with brown hairs. Thorax (Fig. 4c). Pronotum brownish yellow. Prescutum brown. Anterior scutum brown with a broad, posteriorly subdivided, dark brown median stripe and a spot on each side of it; posterior scutum brownish black with a broad yellow median stripe. Scutellum brownish black with a broad yellow median stripe. Mediotergite brownish black with a narrow yellow median stripe. Pleura (Fig. 4a) brownish yellow with a broad, anteriorly indistinct, brownish black stripe extending from cervical region to mediotergite. Hairs on thorax white. Coxae brownish yellow; trochanters yellow; femora brownish yellow with subtips brownish black; tibiae brownish yellow with tips narrowly brownish black; tarsi brownish yellow with tips brownish black. Hairs on legs dark brown. Wing (Fig. 4d) tinged with pale brownish yellow. Many dark patches around cross veins and portions of longitudinal veins as well as patches in cells as shown in Fig. 4d; four darker spots at base of wing, at base of Rs, at fork of Sc, and over R 2 and tip of Sc 2 , the latter two spots connected by a narrow stripe along Sc 2 . Venation: Sc long, ending far beyond fork of Rs and at 1/3 of cell dm. Basal section of Sc 2 near tip of Sc 1 . Tip of Sc 2 nearly transverse, indistinct at wing margin. Rs very short, slightly sinuous. R 2 before tip of Sc 2 and distance between them about length of R 2 . Radial and medial veins distinctly curved caudally before wing margin. Crossvein r-r at basal 1/3 of cell r 3 . Cell dm elongate, more than 5 times as long as its width; m-m elongate, twice as long as basal section of M 3 . Basal section of CuA 1 far beyond fork of M and at about 1/4 of cell dm. A 1 straight, slightly curved near tip. A 2 slightly sinuous. Halter length 1.5 mm, pale yellow with knob brownish black.
Abdomen. Tergites brownish yellow with lateral borders brownish black. Sternites brownish yellow, middle of first sternite paler. Hairs on abdomen white. Hypopygium (Fig. 5). Ninth tergite with rounded posterior margin and small median emargination. Gonocoxite stubby with an elongate, blunt-apexed ventromesal lobe; inside edge with a large setose bulge. Outer gonostylus arched at 2/3 length, tip acute. Inner gonostylus short, oval with a long arched rostral prolongation armed with two spines at base from a single tubercle; an elongate lobe arising dorsally near base with a brush of long setae at apex, at right angle to lobe and directed laterally. Paramere wide at base, elongate, triangular distally. Penis long, tip sunken in the middle.
Female. Unknown. Distribution. China (Yunnan); India. Remarks. This species was known previously only from India. Now it is recorded from China for the first time.