New species of Myolepta Newman, 1838 (Diptera, Syrphidae) from the Indomalayan Realm

. Three new species of Myolepta Newman, 1838 are described from Thailand ( M. iota sp. nov.), Laos ( M. diaphora sp. nov.) and Indonesia ( M. geras sp. nov. from Java), and new records of Myolepta petiolata Thompson, 1971 from Thailand are also provided. Diagnoses, illustrations and known distributional data are given. In addition, the generic affinities and subdivision of Myolepta are discussed based on these newly described taxa.


Introduction
Myolepta Newman, 1838 is a genus of small to medium-sized (5-12 mm) flower flies (Diptera, Syrphidae) present in all biogeographic realms except Australasia (Thompson & Vockeroth 1989;Reemer et al. 2005). There currently are 45 described species of Myolepta: three from the Afrotropics, seven Nearctic species, 12 from the Neotropical Realm, 17 from the Palaearctic, and six from the Indomalayan Realm Thompson 2014;Gilasian et al. 2016;van Steenis 2020;Hassan et al. 2021). These flies can be easily identified by the presence of strong ventral setae (usually referred to as spines) on all femora, which are more or less swollen, males with a distinct facial tubercle and females without facial tubercle (concave face), and the placement of the crossvein r-m in the basal half of the cell dm.
In the present study three new Indomalayan species of Myolepta are described from Thailand, Laos and Indonesia (Java), and new records of Myolepta petiolata Thompson, 1971 are also given. In addition, the generic affinities and subdivision of Myolepta are discussed based on these new described taxa.

Material and methods
Morphological terminology follows Cumming & Wood (2017). Thompson et al. (2017) was used to determine the genus and the identification keys by Thompson (2014) and Hassan et al. (2021) were utilized for species determination. Then, specimens were compared against digital images of the type specimens of the already published Indomalayan species of Myolepta.
Images of the syntypes (female and male) of Myolepta himalayana Brunetti, 1915 can be accessed using the Faunal Information System of the Zoological Survey of India, at https://zsifis.nic.in/ImageRequest/GetByCategory/14. Images of the holotype male of Myolepta graciliventris Wiegmann, 1986 are available from http://n2t.net/ark:/65665/333808d3a-e7cf-406c-adb5-257f19ce8794 (see also Fig. 2). Thompson (2014) Thompson, 1971 (red open square), M. petiolata Thompson, 1971 (black circle), and M. splendens Thompson, 2014 (light brown circle). provided good-resolution images for the holotype male of Myolepta splendens Thompson, 2014, andHassan et al. (2021) did the same for the holotype male of Myolepta mahmoodii Hassan & Bodlah, 2021in Hassan et al. 2021. For the type material of Myolepta orientalis Thompson, 1971 and Myolepta petiolata Thompson, 1971, Jeremy Frank (Bernice Pauahi Bishop Museum, Honolulu, USA) kindly photographed the holotype female of both taxa and shared the images for publication (Fig. 3D-F). Permission to reproduce images of the type material was not granted by the Zoological Survey of India, neither for the publications of Thompson (2014) and Hassan et al. (2021); thus, referencing the aforementioned Faunal Information System and publications is recommended when the provided identification key is used.
All measurements were taken using a reticule in a Leica® M165C microscope.
Body length was measured from the anterior oral margin to the posterior end of the abdomen, in lateral view. Wing length was measured from the wing tip to the basicosta.
Focus stacked images were created using the software Zerene Stacker® ver. 1.04 (Richland, Washington, USA), based on photographs of pinned specimens taken with a Canon EOS 7D® camera mounted on a P-51 Cam-Lift (Dun Inc., VA, USA) and with the help of Adobe Lightroom ® ver. 5.6. Later, stacked images were edited with Adobe Photoshop ® ver. CS5.1. Figure 1 was created with the help of SimpleMappr (Shorthouse 2010).

Diagnosis
Black, medium-sized species of Myolepta, with lateral white pruinosity on face, long facial sulcus and elongated postpedicel (Fig. 3C). Frontal prominence produced forward and vertex protuberant. Thorax and abdomen conspicuously punctate. Scutum mostly black, very lightly white pruinose except dense white pruinose on transverse suture and remarkable thick white hairs on notopleuron, posterodorsal anterior anepisternum, posterior anepisternum, anterior anepimeron and dorsal part of katepisternum. Wing largely bare basally, with vein R 4+5 with last section (petiole) shorther than crossvein h. Legs bicolorous (Fig. 3A,C). Abdomen constricted at the base of tergite 2, black with a golden tomentose fascia on the posterior margin of tergite 3, and tergite 4 with a medial patch of adpressed, longer, golden hairs ( Fig. 3A-B).

Differential diagnosis
Myolepta diaphora sp. nov. can be distinguished from other species of Myolepta of the Indomalayan Realm by having the abdomen basally constricted (only M. petiolata has the abdomen petiolate, less than half its maximum width at its minimum), legs bicolorous (legs entirely pale yellow in M. splendens) and elongated postpedicel. It differs from M. graciliventris by the face shiny medially (entirely golden pruinose in M. graciliventris) and abdominal tergite 2 broader than long (tergite 2 longer than broad in M. graciliventris). It is very similar to M. orientalis, but differs by having femora and tibia partly yellow (metallic bluish-black in M. orientalis; Fig. 3D-E), abdominal tergite 3 only with a narrow, dense golden pruinose fascia on posterior margin (tergite 3 black with a medial golden hairy vitta broadening posteriorly in M. orientalis; Fig. 3D), and tergite 4 black with a medial patch of adpressed golden hairs (tergite 4 black basally and orange on apical ⅓, completely covered with golden hairs in M. orientalis; Fig. 3D).  Thompson, 1971, ♀, holotype (BPBM). D. Habitus, lateral view. E. Habitus, dorsal view. F. Head, frontal view. Scale bars: A-C = 1 mm.

Female
Head (Fig. 3C). Face concave, without facial tubercle, black, shiny medially with very light white pruinosity, dense white pruinose laterally, with some scattered white hairs. White facial pruinosity does not reach antennal insertion level dorsally and expands towards oral margin ventrally, anterior to gena, but it does not reach the oral margin. Gena shiny black ventral to facial sulcus, white pruinose between facial sulcus and eye, with some scattered white pile. Lunule yellow. Frontal prominence conspicuous, produced forward. Frons black, with some scattered white hairs, depressed medially in the area above lunule with vertex protuberant; shiny on ventral ⅓, with two large golden-white pruinose maculae in middle ⅓, light white pruinose medially and dorsally until the anterior ocellus. Vertical triangle shiny black with yellow hairs. Eye bare, dichoptic. Antenna light brown except postpedicel black on dorsal ½ and yellow on ventral ½; postpedicel furry-like, rounded apically, slightly longer than broad, elongated, more than 2 × as long as broad. Arista bare, brown. Occiput covered with silvery pruinosity (except posterior margin of vertical triangle), with white hairs ventrally. tHorax ( Fig. 3A-B). Scutum black except postpronotum and postalar callus yellowish anteriorly and posteriorly, punctate, very lightly white pruinose except dense white pruinose on transverse suture, with adpressed, short white-yellowish hairs, which are thicker on the notopleuron. Scutellum rounded with preapical sulcus, punctate, with adpressed, short white-yellowish hairs, black except yellow preapical sulcus. Pleuron black, very lightly white-grey pruinose except densely white-grey pruinose on posterior anepisternum and medial and posterior parts of katepisternum, with thick white hairs on posterodorsal anterior anepisternum, posterior anepisternum, anterior anepimeron and dorsal part of katepisternum; katerpisternal hair patches broadly separated. Plumule yellow, very short. Metaepisternum and metasternum bare. Halter yellow, brownish basally. Posterior spiracular fringes dark brown.
Wings. Membrane hyaline; pterostigma brown basally becoming hyaline apically; extensively microtrichose except cell c on basal ¾, cells r 1 and br anterior to RS bifurcation, and cells bm and cua on basal ¾. Spurious vein absent. Vein RS and basal section of R with black setulae dorsally. Cell r 4+5 closed very close to the wing margin; vein R 4+5 with last section (petiole) shorther than crossvein h ( Fig. 3A-B).
Legs. Coxae black except fore coxa yellow ventrally, densely grey pruinose. Fore and mid trochanter yellow; hind trochanter brown, yellow apically. Fore femur incrassate, yellow on basal 2 /5-½ and black on apical ½-3 /5, with yellow hairs and two rows of black setae on ventral side; fore tibia yellow on basal ¼, black on apical ¾, yellow hairy with black setulae on ventral side; fore basitarsomere yellow, yellow hairy; second fore tarsomere yellow on basal ¾ and black on apical ¼, yellow hairy; three apical fore tarsomeres black, black hairy. Mid femur slightly swollen, yellow on basal 2 /5 and black on apical 3 /5, with yellow hairs and two rows of black setae on ventral side; mid tibia on basal ¼, black on apical ¾, yellow hairy with black setulae on ventral side; two basal mid tarsomeres yellow, yellow hairy; apical with some black setulae; three apical mid tarsomeres black, black hairy. Hind femur incrassate, yellow on basal 2 /5 and black on apical 3 /5, with yellow hairs and two rows of black setae on ventral side; hind tibia yellow on basal ½, black on apical ½, yellow hairy with black setulae on ventral side; hind basitarsomere yellow, yellow hairy; second hind tarsomere yellow on basal ¾ and black on apical ¼, yellow hairy; three apical hind tarsomeres black, black hairy. All tibiae narrower basally and broader apically, remarkably hind tibia basally almost half as broad as apically. abdoMen ( Fig. 3A-B). Punctate, constricted basally with anterior margin of tergite 2 narrower than thorax (narrowest point of abdomen until posterior half of tergite 4). Tergite 1 black, lightly grey pruinose medially and densely grey pruinose laterally, white pilose. Tergite 2 black, with adpressed hairs that are black medially and white laterally, with long white hairs on anterolateral corner. Tergite 3 black, with narrow, golden tomentose fascia on posterior margin, with adpressed medially black and laterally white hairs, with narrow patch of adpressed golden hairs posteromedially, anterior to tomentose fascia. Tergite 4 black, with posterior margin dark brown, with adpressed black hairs except patch of adpressed, thicker, longer golden hairs in middle of tergite.

Remark
The holotype female was collected in primary mountain forest. Diagnosis Myolepta geras sp. nov. has short antenna, shorter than face, with postpedicel less than 2 × longer than broad (Fig. 4C). Face black, shiny medially, with grey pruinosity along the eye margin ( Fig. 4C). Black scutum with adpressed black hairs mixed with yellow scale-like hairs. Legs bicolorous (Fig. 4A). Cell r 4+5 distinctly petiolate; vein R 4+5 with last section longer than crossvein h (Fig. 4B). Abdomen parallel-sided, tergites 2 and 3 black, pruinose, with two elongated orange maculae on anterior margin not reaching the posterior margin, and tergite 4 black with posterior margin brown, shiny except a medial brown pruinose macula on anterior margin ( Fig. 4A-B).

Differential diagnosis
Myolepta geras sp. nov. differs from other Indomalayan species of Myolepta (except Myolepta iota sp. nov.) by the presence of scale-like hairs on the scutum and pleuron ( Fig. 4A-B), and by the cell r 4+5 distinctly petiolate, with petiole longer than crossvein h (Fig. 4B). It differs from Myolepta iota sp. nov. by the coloration of the legs (see identification key), the shiny anterodorsal part of the anterior anepisternum not covered with scale-like hairs (grey pruinose in Myolepta iota sp. nov.), the absence of scale-like hairs on scutellum (present in Myolepta iota sp. nov.), abdominal pattern, and the membrane between tergites and sternites partly black (entirely yellow in Myolepta iota sp. nov.). Male genitalia quite similar to those of Myolepta iota sp. nov., but different in the dorsal margin of the surstylus and the size and arrangement of the lateral setae on the hypandrium (see Figs 4-5).

Etymology
From Greek 'γῆρᾰς' ('gêras'), meaning 'old age' (Brown 1956: 569); it refers to the age of the specimen, which was collected 90 years ago. Species epithet is to be treated as a name in apposition.

Type locality
Indonesia

Male
Head (Fig. 4A, C). Face with small facial tubercle, bare medially, shiny black, densely silvery pruinose laterally along eye margin from the antennal insertion to gena (pruinosity continuing until the occiput) with scattered thick white hairs, and lightly grey pruinose above antennal insertion. Gena narrow, shiny black and bare ventrally, dorsally completely silvery pruinose and with scattered thick white hairs. Lunule shiny black, dark brown medially. Frontal triangle shiny black on ventral ½, silvery pruinose on dorsal ½; pruinosity from dorsal part of frontal triangle not joining with lateral pruinosity of face. Eye bare, with slightly enlarged ommatidia on dorsofrontal part; holoptic. Eye contiguity longer than frontal triangle. Antenna yellow; scape and pedicel with yellow hairs and 2 and 3 brown setulae dorsally, respectively; postpedicel furry-like, rounded apically, slightly longer than broad. Arista bare, brown. Vertical triangle black, shiny, with adpressed yellow setulae. Occiput covered with silvery pruinosity (except the posterior margin of vertical triangle), with white hairs ventrally and scattered short, black setulae along margin, more abundant on dorsal ⅓. tHorax ( Fig. 4-B). Scutum black, densely grey pruinose anteriorly, including anterior ½ of postpronotum, lightly grey pruinose on notopleuron. Postalar callus and posterior part of postpronotum brown. Scutum with adpressed black hairs mixed with scale-like hairs, which are dark yellow and more dense anterior to transverse suture and white and more scattered posterior to transverse suture. Short black setulae on supra-alar area. Scutellum rounded, black, without subscutellar fringe, with adpressed yellow hairs; posterior margin with short black setulae with thick, expanded alveolus, making posterior margin to look serrate. Pleuron black, with grey dense pruinosity on proepisternum and proepimeron; with white scale-like hairs on posterodorsal part of anterior anepisternum, posterior anepisternum, dorsal part of katepisternum and anterior anepimeron (posterior anepimeron with 1-2 white scale-like hairs anteriorly); anatergum with yellow hairs, lightly grey pruinose. Plumule yellow, very short. Metaepisternum and metasternum bare. Halter yellow, brownish basally. Posterior spiracular fringes dark yellow to brown.
Wings. Membrane hyaline; pterostigma yellow; extensively microtrichose except cell c on basal ¼, cell br anterior to RS bifurcation, and cells bm and cua on basal ¾. Spurious vein absent. Vein RS and basal section of R with black setulae dorsally. Cell r 4+5 petiolate; vein R 4+5 with last section longer than crossvein h and slightly shorter than crossvein r-m.
Legs. Coxae black (fore coxa yellowish ventrally), partly lightly grey pruinose; trochanters yellow. Fore femur incrassate, yellow except black on apex forming subapical black ring, with yellow hairs and two rows of short black setae on ventral side; fore tibia yellow on basal ⅔, black on apical ⅓, yellow hairy with black setulae on ventral side; basal three fore tarsomeres black with dorsal part yellow, black hairy dorsally and yellow hairy ventrally with some black setulae; apical two fore tarsomeres black with yellow hairs; apical tarsomere yellowish at apex. Mid femur slightly swollen, yellow except black on apex forming a subapical black ring, with yellow hairs and two rows of short black setae on ventral side; mid tibia yellow, yellow hairy with black setulae on ventral side; basal three mid tarsomeres yellow, apical two mid tarsomeres black, black hairy dorsally and yellow hairy ventrally with some black setulae. Hind femur yellow on basal ⅓, black on apical ⅔, yellow hairy with two rows of short black setae on ventral side, and 4-5 long (half as long as femur's width), yellow setae on dorsal side; hind tibia yellow on basal ½, black on apical ½, yellow hairy with black setulae on ventral side; hind basitarsomere yellow, black and yellow hairy dorsally and yellow hairy ventrally. abdoMen ( Fig. 4A-B). Parallel-sided, unmargined. Tergite 1 black, grey pruinose, yellow-white hairy. Tergite 2 black, with two lateral elongated orange maculae on anterior margin not reaching lateral or posterior margins, lightly grey pollinose (clearly visible along anterior margin), with adpressed black hairs medial and laterally, with a group of 6-7 long, yellow setae on anterolateral margin. Tergite 3 black, with two lateral elongated orange maculae on anterior margin not reaching lateral or posterior margins, lightly grey pollinose (clearly visible along anterior margin) but shiny on posterior margin and lateral margins, with adpressed black hairs medial and laterally. Tergite 4 black, shiny with some light grey pruinose on anterior margin, with adpressed golden-brownish hairs. Sternites black except sternites 2 and 3 brown, with short yellow hairs, shiny except sternite 1 entirely grey pruinose and sternite 4 with medial grey pruinose vitta. Membrane between tergites and sternites 2 and 3 black, between tergite and sternite 4 yellow.

Remarks
The original label states "Dungus Iwul" as the sampling locality of the holotype, and I assume this refers to the Dungus Iwul Nature Reserve in West Java province. This is the single species of Myolepta known from Indonesia, representing the southernmost record of this genus in the Indomalayan Realm.

Differential diagnosis
Small species of Myolepta that differs from other Indomalayan species of Myolepta (except Myolepta geras sp. nov.) by the presence of scale-like hairs on scutum, pleuron and scutellum, and by the cell r 4+5 distinctly petiolate, with petiole longer than crossvein h. It differs from Myolepta geras sp. nov. by the coloration of the legs (see identification key), the grey pruinosity on the anterior part of the anterior anepisternum not covered with scale-like hairs (shiny in Myolepta geras sp. nov.), the presence of scale-like hairs on scutellum (absent in Myolepta geras sp. nov.), and the membrane between tergites and sternites entirely yellow (partly black in Myolepta geras sp. nov.). Male genitalia quite similar to those of Myolepta geras sp. nov., but different in the dorsal margin of the surstylus and the size and arrangement of the lateral setae on the hypandrium (see Figs 4-5).

Etymology
From Greek 'ἰῶτα' ('iôta'), the name of the ninth letter of the Greek alphabet and used to name anything very small (Brown 1956: 488). Species epithet is to be treated as a name in apposition. Paratype THAILAND • 1 ♂; same collection data as for holotype; ZFMK; ZFMK-DIP-00082515.

Male
Head (Fig. 5C). Face with a small facial tubercle, bare medially, shiny black, densely silvery pruinose laterally along eye margin from antennal insertion to gena (pruinosity continuing until occiput) with scattered thick white hairs, and lightly grey pruinose above antennal insertion. Gena narrow, shiny black and bare ventrally, dorsally completely silvery pruinose and with scattered thick white hairs. Lunule shiny brown. Frontal triangle shiny black on ventral ½, silvery-grey pruinose on dorsal ½; pruinosity from dorsal part of frontal triangle not joining with lateral pruinosity of face. Eye bare, with slightly enlarged ommatidia on dorsofrontal part; holoptic. Eye contiguity as long as frontal triangle. Antenna yellow; scape and pedicel with yellow hairs; pedicel with 3 brown setulae dorsally; postpedicel furry-like, rounded apically, longer than broad. Arista bare, brown. Vertical triangle black, shiny, with adpressed yellow setulae. Occiput covered with silvery pruinosity (except the posterior margin of the vertical triangle), with white hairs ventrally and scattered short, black setulae along margin, more abundant on dorsal ⅓. tHorax (Fig. 5A-B). Scutum black, densely grey pruinose anteriorly, including anterior ½ of postpronotum. Postalar callus brown. Scutum with adpressed black hairs mixed with yellow scale-like hairs. Short black setulae on supra-alar area. Scutellum rounded, black, without subscutellar fringe, with adpressed yellow hairs mixed with yellow scale-like hairs; posterior margin with short black setulae with thick, expanded alveolus, making the posterior margin to look serrate. Pleuron black, with grey dense pruinosity on proepisternum, proepimeron and anterior bare part of the anterior anepisternum; with white scale-like hairs on posterodorsal part of the anterior anepisternum, posterior anepisternum, dorsal part of katepisternum and anterior anepimeron (posterior anepimeron with 2-3 white scalelike hairs anteriorly); anatergum with yellow hairs, lightly grey pruinose. Plumule yellow, very short. Metaepisternum and metasternum bare. Halter yellow. Posterior spiracular fringes yellow. Wings. Membrane hyaline; pterostigma yellow; extensively microtrichose except cell c on basal ⅓, cell br anterior to RS bifurcation, cell bm on basal ¾ and cell cua on basal ½. Spurious vein absent. Vein RS and basal section of R with black setulae dorsally. Cell r 4+5 petiolate; vein R 4+5 with last section longer than crossvein r-m.
Legs. Coxae black; fore coxa densely grey pruinose; trochanters yellow. Fore femur incrassate, yellow on basal ½-3/5 and black on apical 2 /5-½, with apex yellow, with yellow hairs and two rows of short black setae on ventral side; fore tibia yellow on basal ⅔ with black elongated macula on posterior side, black on apical ⅓, yellow hairy with black setulae on ventral side; basal three fore tarsomeres yellow with black hairs dorsally, black with yellow hairs ventrally; apical two fore tarsomeres black with yellow hairs. Mid femur slightly swollen, yellow on basal 4 /5 and black on apical 1 /5, with yellow hairs and two rows of short black setae on ventral side; mid tibia yellow, yellow hairy with black setulae on ventral side; basal three mid tarsomeres yellow, apical two mid tarsomeres black, black hairy dorsally and yellow hairy ventrally with some black setulae. Hind femur yellow on basal ⅓, black on apical ⅔, yellow hairy with two rows of short black setae on ventral side, and long (half as long as femur's width) black setae on the dorsal side; hind tibia yellow on basal ⅔, black on apical ⅓, yellow hairy with black setulae on ventral side; basal three hind basitarsomeres yellow, yellow hairy, and apical two hind basitarsomeres black, black and yellow hairy. abdoMen ( Fig. 5A-B). Almost parallel-sided, with the maximum width between tergites 3 and 4, unmargined. Tergite 1 dark brown, brown pruinose, yellow hairy; tergite 2 broader than long, brown with diffuse yellow fascia on anterior margin broadening laterally, brown pruinose, yellow hairy with tuft of long yellow setae on anterolateral corner; tergite 3 brown becoming black posteriorly with diffuse yellow marking on anterior margin, brown pruinose, yellow hairy; tergite 4 black with posterior margin brown, shiny except medial, triangular brown pruinose macula on anterior margin, yellowish brown hairy. Sternites with addressed yellow hairs; sternite 1 dark brown to black, densely grey pruinose; sternite 2 dark brown medially and yellow laterally; sternite 3 dark brown with two yellow macula anterolaterally; sternite 4 dark brown. Membrane between tergites and sternites entirely yellow.
MaLe genitaLia. As in Fig. 5D-I. Epandrium subquadrate; surstylus with dorsal margin strongly undulate forming two clear lobes, with strong setae (Fig. 5F); hypandrium with 4-5 small and thin setae at margin (on rim) between dorsal and lateral parts plus three additional small setae at lowest part of this rim in the dorsal part.

Remark
I assume that these specimens were collected with a Malaise trap, based on the sampling dates, and that it co-occurs with Myolepta petiolata. Thompson, 1971 Fig. 6

Diagnosis
Black Myolepta species with long antenna, as long as face, with elongated postpedicel (Fig. 6C, F). Black body with a yellow pruinose fascia on posterior margin of tergite 3, and black legs, except basal 1 /5-¼ of femora yellow, fore basotarsomere yellow and two basal mid tarsomeres yellow (Fig. 6). Scutellum orange. Pterostigma dark brown with apical part hyaline. Cell r 4+5 closed at wing margin, with petiole shorter than crossvein h. Abdomen strongly petiolate, less than half its maximum width at its minimum (on tergite 2).

Differential diagnosis
Myolepta petiolata differs from all other described species of Myolepta by the strongly petiolate abdomen, which is less than half its maximum width at its minimum (Fig. 6B, E). It differs from all other Indomalayan species of Myolepta by the orange scutellum (bicolorous or black in other species).

Type locality
Thailand

Remarks
No male specimen is known of this species. These are the first published records of this species after its original description, and the new record locality is 105 km west of the type locality. I assume that the specimens were collected with a Malaise trap, based on the sampling dates, and that it co-occurs with Myolepta iota sp. nov. Thompson (1971) described this species and Myolepta orientalis from the same locality and date; thus, I deduce that M. petiolata and M. orientalis also co-occur.

Generic affinities and subdivision of Myolepta
The current generic concept of Myolepta derives from the diagnosis made by Shannon (1922): small dark flies; face concave in the females, but tuberculate in males; antennae short; abdomen short oval; scutellum with preapical margin; femora moderately swollen with short spines ventrally; wing cell r 4+5 not petiolate and veins R 4+5 and M 1 meet close to the apex of the wing. Within his Cheilosinae, Shannon (1922) defined the tribe Myoleptini [as Myioleptini] by the last section of vein R 4+5 (= petiole) shorter than crossvein r-m; another way of saying that cell r 4+5 has an acute distal corner, close to the wing margin. From the identification key by Shannon (1922), it is clear that he considered the genera Myolepta, Eumyiolepta Shannon, 1921 (now a junior synonym of Myolepta) and Apicomyia Shannon, 1922 (now a junior synonym of Cynorhinella Curran, 1922) as members of the Myoleptini. Later, Hull (1949) moved Cynorhinella to his Cheilosini and left Myolepta in Myoleptini, together with a fossil genus. Within Myolepta, Hull (1949) recognized four subgenera: Myolepta sensu stricto, Eumyiolepta (species with scale-like hairs), Sericolepta Hull, 1945 (fossil subgenus with cell r 4+5 closed quite some distance from the wing margin, petiolate, scutellum without preapical margin and numerous ventral setae on hind femora), and Arctolepta Hull, 1945 (fossil subgenus with setae on the scutellum, cell r 4+5 with a long petiole and "hind femora stout with many bristly spines").
At the same time, Hull (1949) placed Lepidomyia (as Lepidostola) in his Chrysogasterini for those peculiar small flies with scale-like hairs; elongated antennae; inconspicuous facial tubercle, sometimes with two tubercles; ventral setae on all femora; hind femur considerably swollen; vein M 1 long, with or without spur, meeting vein R 4+5 at wing apex. Hull (1949) created the subgenus Protolepidostola Hull, 1949 for his species Lepidostola scintillans Hull, 1946 (now Myolepta scintillans) characterized by the short, oval postpedicel. Thompson (1968) defined his concept for Myoleptini and provided a historical view of Protolepidostola, besides describing two new species of Protolepidostola. He divided Myolepta into three subgenera (Myolepta, Eumyiolepta and Protolepidostola) and pointed out several diagnostic characteristics for Protolepidostola: short head compressed antero-posteriorly; small, compact flies with scale-like hairs present; reduced occiput laterally; cell r 4+5 acute and drawn out to the wing margin; and spurious vein absent.
A few years later, Thompson (1972) placed Lepidomyia and Myolepta (now with only two subgenera: Myolepta and Protolepidostola) in his new concept of Chrysogasterini, together with another group of genera, different from those of his Myoleptini from 1968. In his definition of the tribe, Thompson (1972: 114) already mentioned numerous exceptions for Chrysogasterini and concluded that Lepidomyia and Myolepta were distinguished by the presence or absence of a facial tubercle in females and the shape of the postpedicel (two or more times as long as broad in Lepidomyia and short, oval in Myolepta). Thompson needed to modify again his concept of Myolepta even before the publication of his PhD [presented in 1970[presented in (Thompson 1970 and finally published in 1972 (Thompson 1972)] when he discovered two new Myolepta species from Thailand with elongated postpedicel (Thompson 1971). Consequently, the differences between Lepidomyia and Myolepta were reduced to the presence of a facial tubercle in the females and restricting Lepidomyia to the New World, from the southern USA (Texas) to Argentina, although it is absent from the Chilean subregion (Thompson et al. 2010).
All these rapid changes in the generic concept of Myolepta culminated with another publication where Thompson (1974) proposed a new subgeneric division. Instead of subgenera, he divided Myolepta into six species groups and suggested the possibility that Lepidomyia could be a species group within Myolepta. Thompson (1974) stated the variability of certain morphological characters within the genus: head shape normal/compressed longitudinally; male holoptic/narrowly dichoptic; fore femora with one/ two rows of setae or without; metasternum pilose/bare; postpedicel oval/elongate; scutellum rounded/ triangular; scutellum with/without preapical sulcus; presence/absence of scale-like hairs; katatergum hairy/bare; cell r 4+5 with very short/long petiole; and abdomen petiolate/oval. It seems that each new species of Myolepta from the Indomalayan Realm is so distinct from the previously known, that it can be assigned to its own species group. This occurred with Myolepta graciliventris, which lacks a prominent facial tubercle in males (another variable diagnostic character to add to the list) and has a petiolated cell r 4+5 (Wiegmann 1986). Similarly, an own separated species group can be argued for M. iota sp. nov. and M. geras sp. nov.
Until now, an elongate postpedicel was found in the Afrotropical species of Myolepta (africana group) and three Indomalayan taxa (M. graciliventris, M. petiolata and M. orientalis); scale-like hairs were diagnostic of the strigilata (= Eumyiolepta), scintillans (= Protolepidostola), africana and orientalis groups; and a long petiole closing cell r 4+5 was only found in the Afrotropical species, M. graciliventris, and Myolepta minuta Fluke, 1956 (a small species from Argentina with dark maculae on the wing). Newly described species M. iota sp. nov. and M. geras sp. nov. do present the long petiole condition and the lack of prominent facial tubercle (males do have a relative small facial tubercle). These two new species do not key out properly to any Indomalayan group using the key to Myolepta species groups by Thompson (1974), as they do not have a preapical sulcus in the scutellum (orientalis group), nor a petiolate abdomen (petiolata group). On the other hand, M. diaphora sp. nov. can be considered a member of the orientalis group, as M. orientalis and M. diaphora sp. nov. are quite similar morphologically as stated earlier.
The support of the species group proposed by Thompson (1974) is not strong as already pointed out by Reemer et al. (2005) and the whole genus needs a re-evaluation of the morphological characters and affinities. In addition, it is necessary to explain more in detail certain morphological characteristics, such as scale-like hairs. Thompson (1974) considered that M. orientalis has scale-like hairs, but hairs in this species are not modified (expanded laterally; flattened with rounded apex) like in M. iota sp. nov. and M. geras sp. nov., and they are just thicker (and mostly longer; with sharp-pointed apex) than the other body hairs, which one could call setulae or setae. These are also present in M. diaphora sp. nov. As an example of how difficult defining these scale-like hairs is, Fluke & Weems (1956) mentioned that the Argentinian Myolepta greenei Hull, 1941 "is a transitional form between Myolepta [with regular body hairs] and Eumyolepta [with scale-like hairs]". Moreover, the new Indomalayan species challenge the use of published identification key even at genus level, as cell r 4+5 without petiole is commonly used in the literature to key out Myolepta .
Although the phylogenetic relationships within the paraphyletic Eristalinae are in need of revision (Mengual et al. 2015;Moran et al. 2022), Myolepta is currently placed in the Brachyopini, subtribe Brachyopina (see http://syrphidae.myspecies.info/node/6170 for the intrafamilial classification based on Thompson's unpublished concepts), but the most recent molecular phylogenetic analysis recovered Myolepta as sister to Volucellini with poor support (Bayesian inference) or as sister to the rest of Eristalinae (Maximum Likelihood) (Moran et al. 2022). In other words, the phylogenetic placement of Myolepta and its generic limits are unclear.

Comments on biology and geographical distribution
The Indomalayan flower flies are clearly understudied. Recent taxonomic revisionary works brought to attention this fact by the high number of new species discovered (Mengual & Ghorpadé 2010;Mengual 2012Mengual , 2016van Steenis & Hippa 2012;Thompson 2013Thompson , 2015Thompson , 2017aThompson , 2017bThompson , 2020 (Vockeroth & Thompson 1987;Thompson & Rotheray 1998;Thompson et al. 2010;Ssymank et al. 2021) and unpublished revisionary works by F.C. Thompson (Thompson 2006 for South America; Thompson et al. unpub. for Australia), except the Indomalayan Realm. Ghorpadé (1994Ghorpadé ( , 2014 covered the flower flies of the Indian subcontinent, but he did not provide identification keys for all the genera, and taxonomists still need to use Brunetti (1923) for Indian flower flies, with the help of the published catalogues (Knutson et al. 1975). For the Malayan part of this realm (Myanmar to Vietnam and Philippines south to Java; see Thompson & Vockeroth 1989) there are no recent taxonomic revisions or identification keys, not even to genus level. More taxonomic work is needed focusing on this part of our planet. This is evident by the fact that the holotype of M. geras sp. nov. was collected 90 years ago and the type material of M. iota sp. nov. 30 years ago, both above the average 21 years of 'shelf life' or the time between the first collection of a specimen of a new species and its formal description and naming in the scientific literature (Fontaine et al. 2012).
As mentioned in the introduction, Myolepta is absent from the Australasian Realm, and Thompson (2014) stated that the genus is absent from "oceanican islands" (he might refer to oceanic or Oceanian islands).
The new species M. geras sp. nov., then, represents the first species of Myolepta from an oceanic island (Java), but the genus has not been reported from Oceania yet. With the new taxa described here, the total number of described species of Myolepta in the Indoamalayan realm is nine. It is important to remark that all Indomalayan species of Myolepta are described based on singletons (seven taxa) or doubletons (M. himalayana and M. iota sp. nov.), and that we only know both sexes of one species (M. himalayana).
A recent publication of a DNA Barcode library from Mount Halimun-Salak (West Java, Indonesia) reports that almost 70% of their BINs (Barcode Index Number; Ratnasingham & Hebert 2013) were singletons and more than 90% had less than five specimens (Cancian de Araujo et al. 2018); their field work ran for eight months using 34 Malaise traps. Among their BINs, only one out of 1149 belonged to Syrphidae. As stated by Lim et al. (2012) "Singletons-species only known from a single specimen -and uniques-species that have only been collected once -are very common in biodiversity samples", especially in tropical areas (Coddington et al. 2009). True rarity, small geographic ranges of the species and problems with logistics of fieldwork, combined with the difficulty of comprehensive sampling, enhance the presence of singletons (Ahrens et al. 2016). Coddington et al. (2009) suggested that the major cause for singletons is the undersampling, but a recent review affirms that additional sampling helps little to eliminate rarity and new fieldwork will sample more singletons (Lim et al. 2012). Kurina & Kirik (2021) advocate to describe new species based on singletons to promote further research on the new taxa rather than keeping the specimen for decades until additional specimens become available. The last argument is valid and appropriate for the present work, where the new species are not described in isolation and an identification key is provided for the Indomalayan species of Myolepta.
Tropical species of Myolepta are not numerous in collections and as explained above, new species are usually based on singletons. There are several reasons for this fact; among them: adult behavior (it is assumed that adults are canopy flyers, but there is little evidence), their larval biology (saproxylic in forest with overmature trees, which are not common in forests anymore) and undersampling in the tropics, as already mentioned. Related to the larval biology of Myolepta, forest management techniques are important for the survival of saproxylic flower flies (Reemer 2005) and traditional silvicultural practices promote the presence of tree rot holes (Sebek et al. 2013). Besides human activities, the tree hollow microhabitats define the diversity and complexity of saproxylic networks (Quinto et al. 2015) and the presence or activity of other taxa groups in a trunk cavity may facilitate or be a pre-requisite for the development of larvae of Myolepta, together with hollow orientation and water content (Sánchez-Galván et al. 2014). In conclusion, more fieldwork is needed to have a true overview of the flower fly diversity in the Indomalayan realm, together with more taxonomic work to understand their diversity, without neglecting that the particular biology of certain taxa may hinder our knowledge.