A taxonomic revision of the genus Asiobaccha Violovitsh (Diptera: Syrphidae)

ABSTRACT The flower fly genus Asiobaccha Violovitsh is revised and 10 new species are described: A. aea Mengual & Thompson, A. albipeza Mengual, A. aquila Thompson & Mengual, A. doesburgi Mengual, A. marissae Mengual, A. maculosa Mengual & Thompson, A. notofasciata Thompson & Mengual, A. samoaensis Mengual, A. selsi Mengual and A. taronja Mengual. Moreover, lectotypes are designated for Baccha semifumosa Meijere, Baccha luteolimbata Meijere, Asiobaccha nubilipennis (Austen), A. praefica (Bezzi), A. virtuosa (Curran) and A. sauteri (Kertész), and a neotype for A. loriae (Meijere) is also designated. New synonyms are proposed: Baccha schistaceifrons Meijere and Baccha semifumosa Meijer are synonymised under Asiobaccha bicolor (Austen); Baccha luteolimbata Meijere is a junior synonym of Asiobaccha tinctiventris (Meijere); Baccha flavipes Doesburg is a junior synonym of Asiobaccha tripartita (Walker); Baccha gigas Curran is a junior synonym of Asiobaccha virtuosa Curran; and the syntypes of Baccha sulica Austen are synonymised under Asiobaccha bicolor (Austen) and Asiobaccha tripartita. Diagnoses, illustrations, synonymies and distributional data are given for all described species. Descriptions of new species as well as an identification key to all known species are also provided. http://zoobank.org/urn:lsid:zoobank.org:pub:6B627B0F-9440-47F1-90F4-9AF4C7308A99

Many species described originally as Baccha currently belong to other syrphid generaas many as 10 different genera (Thompson 2013).  established a new subgenus of Baccha for those species with a pilose postpronotum, Allobaccha , and indicated that this new subgenus was not present in the New World.
Since Peck's work (1988), this taxon is considered a valid genus, and this is supported by recent molecular analyses (Mengual et al. 2008Mengual 2015). Later, Hull (1949aHull ( , 1949b divided the genus Baccha into several groups, most of them only found in the Neotropical Region. Asiobaccha was proposed by Violovitsh (1976) as a subgenus of Baccha for Baccha nubilipennis Austen, 1893. He used the postmetacoxal bridge to separate the two subgenera as follows: Asiobaccha species have an incomplete postmetacoxal bridge, presenting a membrane behind metacoxae and sternite 1 reduced, while Baccha has a wellsclerotised postmetacoxal bridge, which means that the metaepisterna are elongated behind the metacoxae and connected medially. Since Violovitsh (1976), Asiobaccha species have been listed as Baccha, as a subgenus of Allobaccha or as Allobaccha, or as a subgenus of Episyrphus Matsumura & Adachi, 1917. During the same period, Allobaccha has been considered a subgenus of Baccha or a valid genus (see Mengual 2015).
Since Thompson and Vockeroth (1989), Asiobaccha has been considered a subgenus of Episyrphus. Based on the difficulty to separate Baccha, Asiobaccha and Allobaccha, Ichige (2009) showed his doubts about placing Asiobaccha nubilipennis under Episyrphus but also pointed out that the genitalia of A. nubilipennis are very different from those of other Bacchini taxa. Recently, molecular studies using three markers, the mitochondrial protein-coding gene cytochrome c oxidase subunit I (COI) gene and the nuclear rRNA 18S and 28S genes (Mengual 2015), resolved that Allobaccha, Baccha and Asiobaccha are not related phylogenetically, and recovered a clade with Asiobaccha together with Episyrphus and Meliscaeva Frey, 1946.

Materials and methods
Differential diagnoses, synonymies and distributions are given for all species included in the study. An asterisk (*) in the distribution statement refers to records from the literature or from Systema Dipterorum (Thompson 2013). New species are described in full, with terminology following Thompson (1999) and Mengual (2012). The abbreviations used for collections follow the standard of the Systema Dipterorum (Thompson 2013), and their equivalents are given below: In the description of type labels, the contents of each label are enclosed in single quotation marks (' '), italics denote handwriting, and the individual lines of data are separated by a double forward slash (//). In the material examined section, the use of ellipses follows standard English practice and merely indicates that the missing information is the same as that in the preceding record. At the end of each record, between square brackets ([]) and separated by commas, the number of specimens and sex, the holding institution, and the unique identifier or number are given.
Google Earth® was used to get the geographic coordinates of the type localities listed in this work. For a few localities in the two Indonesian provinces of New Guinea, the available gazetteer from The Papua Insects Foundation was used to provide the exact location or details (http://www.papua-insects.nl/gazetteer/gazetteer.htm).
All measurements are in millimetres and were taken using a reticule in a Leica® M165 C microscope. Photographs were composed using the software Zerene Stacker® 1.04 (Richland, Washington, USA), based on images of pinned specimens taken with a Canon EOS 7D® mounted on a P-51 Cam-Lift (Dun Inc., VA, USA) and with the help of Adobe Lightroom® (version 5.6). 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.

Geographical distribution
Asiobaccha species are distributed in the Oriental, Australian and Oceanian Zoogeographic Regions, extending into the Sino-Japanese Region sensu Holt et al. (2013). The species with the largest distribution is Asiobaccha nubilipennis, which occurs from Sri Lanka and India northwards to China and Japan, and south to Indonesia (Sumatra, Java, Sulawesi). However, the genus Asiobaccha is present farther south to Australia and New Caledonia, and eastwards to Fiji, Tonga, Tuvalu and Samoa, including

Natural history
Although nothing has been published about the biology of the adults, the author assumes that imagoes of Asiobaccha feed on pollen and nectar like many other syrphid adults, a fact corroborated by field observations (J. Skevington and A. Young, personal comments).
Very little is known about the immature stages of Asiobaccha. Muraleedharan and Radhakrishnan (1986) reported larvae of A. nubilipennis feeding on Aphis (Toxoptera) aurantii Boyer de Fonscolombe, 1841 (Hemiptera: Aphididae) in tea plantations in Anamallai Hills, India. Additionally, Radhakrishnan and Muraleedharan (1993) gave more details of the immature biology of A. nubilipennis, such as aphid consumption and larval stages duration, reared from A. aurantii from southern India. In New South Wales (Australia), Carver et al. (2003) found a second-instar larva of Asiobaccha notofasciata sp. nov. feeding on Aphis (Aphis) clerodendri Matsumura, 1917 (Hemiptera: Aphididae) in a pseudogall of Clerodendrum tomentosum (Vent.) R.Br.

Systematics
Violovitsh (1976) and  described Asiobaccha and Allobaccha as subgenera of Baccha respectively, but only Baccha sensu stricto belongs to the tribe Bacchini (Mengual et al. 2008;Mengual 2015). Based on recent molecular analyses Figure 2. World distribution of Asiobaccha Violovitsh. The limit shown is only an approximation defined by collecting points for specimens examined and literature records. (Mengual 2015), the aforementioned three taxa are not related phylogenetically as suggested earlier and Asiobaccha and Allobaccha are related with other Syrphini genera (Vockeroth 1969;Thompson and Rotheray 1998;Ichige 2009). Each of these three taxa belongs to a separate evolutionary lineage within Syrphinae, and Asiobaccha is close to Episyrphus and Meliscaeva. Mengual (2015) recognised Asiobaccha as a valid genus based on morphological characters and the molecular analyses performed.

Remarks
A total of 19 species are recognised in this revisionary work, with 10 species new to science described here. There are species with more morphological affinities to others that may form species groups, for example A. albipeza sp. nov., A. selsi sp. nov., A. praefica and A. samoaensis sp. nov. with black abdomens; species related to A. nubilipennis with a mesonotal fringe, such as A. aea sp. nov., A. virtuosa, A. doesburgi sp. nov., A. aquila sp. nov. and A. bimaculata (Keiser, 1952); or species with the same abdominal pattern and without mesonotal fringe, such as A. loriae, A. tripartita and A. bicolor. None of these groupings deserves a supraspecific category. On the other hand, male genitalia among Asiobaccha species show subtle differences, except for A. taronja with very large male genitalia and modified sterna (Figure 13a-d).
Female. Similar to male except for normal sexual dimorphism and as follows: face yellow pilose ventrally, frons grey pollinose, and scutellum yellow pilose.

Geographical distribution
Species known from Solomon Islands.

Etymology
The name aea is an arbitrary combination of letters and is to be treated as feminine.

Differential diagnosis
Species with a mesonotal fringe well developed, broad alula and wing entirely microtrichose, which is dark brown even basally with hyaline apical tip. This new species is similar in overall appearance to A. bicolor or A. loriae, but A. aea has an entire microtrichose wing and a mesonotal collar. It can be distinguished from A. nubilipennis and morphologically close species by the wing microtrichia.

Remarks
The female specimen in the USNM was identified as Episyrphus 74-28 Thompson, in litt.
Abdomen. Petiolate, unmargined, black with bluish iridescence, mainly black pilose except tergum 1 pale pilose, with a black pollinose pattern as follows: terga 2-4 with a black pollinose fascia on posterior margin, tergum 2 also with a narrow basal fascia and a medial, small macula of black pollinosity (Figure 3c, d); sterna 2-4 black with bluish iridescence with a black pollinose fascia on posterior margin; male genitalia black.
Female. Similar to male except for normal sexual dimorphism and as follows: frons black, shiny, with white pollinosity on eye margin until half-way between antennal insertion and anterior ocellus; ocellar triangle black, shiny.
Variation. Some paler specimens have pro-and mesofemora yellowish on apical 1/2 and pro-and mesotibiae yellowish on basal 1/2. Other specimens may have a darker face.

Geographical distribution
Species known from Solomon Islands archipelago, including Bougainville Island.

Etymology
The specific epithet is derived from the Latin albus meaning white (Brown 1956, p. 77) and the Greek peza meaning foot (Brown 1956, p. 343), and it refers to the white metatarsi. Species epithet is to be treated as adjective.

Differential diagnosis
Species with the alula narrower than cell BM, and with the abdomen and the scutellum dark, without pale markings. It can be distinguished from A. praefica and A. samoaensis by the narrow alula and the white metatarsus. Description Male: Head. Face with distinct facial tubercle, dark brown becoming orangish-yellow medially, densely silver pollinose, yellow pilose ventrally and black pilose dorsally ( Figure 4e); gena dark brown to black with oral margin paler; lunule yellow, yellow also between antennal bases; frons protruded forward, black with anterior M-shaped yellow macula, black pilose, golden-brownish pollinose posteriorly, shiny black medially; vertical triangle narrow, isosceles (more than four times as long as broad), with the ocelli on the anterior half, black, black pilose; antenna orangish-yellow, black pilose; arista dark brown, bare; eye bare, holoptic; occiput black, grey-silver pollinose, yellowish-white pilose on ventral 2/3 and black pilose on dorsal 1/3.
Wing: membrane dark, infuscated, except basally and apically; stigma brown; extensively microtrichose, except cell R bare basal to vein RS, cell BM bare on basal 1/2, and cell CuP and anal lobe bare basally. Alula present, broader than costal cell, bare with microtrichia on anteroapical quarter. Legs: coxae and trochanters black, pro-and mesoleg yellow, yellow pilose; metafemur yellow but somewhat dark apically, metatibia and metatarsus black.
Variation. Colouration of the metafemur is variable; some specimens have metafemur dark on apical 2/3 and other specimens have it mostly yellow.

Geographical distribution
Species known from the Philippines.

Etymology
The specific epithet is derived from the Latin aquilus meaning dark coloured, blackish (Brown 1956, p. 148). Species epithet is to be treated as adjective.

Differential diagnosis
Species with a yellow face (Figure 4f), alula bare, narrower than costal cell, wing partly bare basally (Figure 14c), and without a mesonotal fringe. The abdominal pattern is identical to another two species with tergum 4 entirely black, A. loriae and A. tripartita, but differs by the wing microtrichia as stated in the key. Asiobaccha bicolor and A. tripartita differ from A. loriae by having the wing bare basally, easy to distinguish because both have always cell CuP and anal lobe partly bare basally (Figure 14c, d); sometimes A. loriae specimens may have very small bare areas in cell BM but cell CuP and anal lobe are always microtrichose (Figure 4c, d). On the other hand, A. tripartita has a more extensive microtrichia and the bare basal areas of the wing are on basal 1/3-1/2 cell BM only (Figure 14d).
Variation. Wing microtrichia is a bit variable in this species, as well as in the close A. tripartita. The bare area of cells BM and R vary between basal 1/2 to basal 3/4 or more for cell BM, and basal 1/3 to basal 1/2 for cell R. Furthermore, a few specimens have costal cell bare very basally. The specimen from New Ireland has the scutum entirely orange. Wing colouration varies from very dark to almost hyaline.

Geographical distribution
Moluccas (Maluku and North Maluku Provinces, Indonesia), New Guinea Island, New Ireland Island, and Australia.

Type locality
Indonesia: West Papua Province, Raja Ampat Regency, Misool Island (Mysol), between 01°40' and 02°04'S, and between 129°43ʹ and 130°26ʹE.   (Walker, 1859)]. The type material of Baccha semifumosa and Baccha schistaceifrons was studied and both species were found to be the same species as bicolor (Austen). Furthermore, one of the syntypes of Baccha sulica was found to also belong to A. bicolor.
This group of species (A. bicolor, A. tripartita and A. loriae) is quite distinct, but the overall morphological similarity makes it difficult to identify each taxon (see Remarks under A. loriae). The author wanted to preserve the recognisable taxa that already had a name, but he is not sure if this is a single very variable species or a complex of many.
Among the studied material, there is another manuscript name referring to a female given by P.H. van Doesburg, Baccha caeruleifrons. This female (Indonesia: Lower Mist Camp, 28 January 1939) is quite different from the other studied specimens: face and frons are white pollinose instead of yellow, white pilose instead of yellow; scutum and pleuron are darker, with not large yellow areas; and wing is less microtrichose, with cells BM and R entirely bare, cell CuP bare on basal 1/2, costal cell bare on basal 1/4 and subcostal cell bare on basal 3/5. The author preferred not to describe a new species based on a single specimen, as this specimen might represent an extreme of a variable species or a different one. Other sources of information (e.g. larval morphology, molecular markers) are needed to solve this morphological variability.
There is another manuscript name from P.H. van Doesburg, Baccha ambonensis (for one male from Ambon, October 1949), which has been never published; thus, it is not available, and refers to a specimen of A. bicolor.

Differential diagnosis
Dark species with yellow face and scutellum (Figure 5a, e), with broad alula, and infuscated wing, which is bare basally (including basal part of cell R) (Figure 5b). It has a well-defined mesonotal collar, and the metatarsus is bicolourous (Figure 5a). The most similar species is A. nubilipennis, but A. bimaculata differs from it by having tergum 3 black with two medial subtriangular yellow maculae, pointing anteriorly and not reaching lateral margins (A. nubilipennis has a complete yellow fascia on tergum 3) and the colour of the pleural pollinosity (golden in bimaculata and white-yellow in nubilipennis).
Another characteristic to separate both species is the colouration of the metafemur; A. bimaculata has the metafemur dark brown with a yellow apex, while A. nubilipennis has a yellow metafemur with a medial dark annulus.

Variation.
A paler specimen has metafemur yellow very basally and apically.
Female. Similar to male except for normal sexual dimorphism and as follows: frons pollinose, ocellar triangle shiny contrasting with frons.
Variation. Some specimens have a medial, small dark macula on the yellow fascia of tergum 3, on anterior margin. Paler specimens have yellow halter and basal 1/2 of metatibia pale.

Geographical distribution
Species known from Papua New Guinea.

Etymology
This species is named after Pieter H. van Doesburg, Sr. (1892 in his honour to acknowledge his work on Syrphidae, especially on this genus. The name is to be treated as a noun in the genitive case.
Female. Similar to male except normal sexual dimorphism and as follows: lunule yellow; frons mostly black, white pollinose with a medial, bare, shiny vitta.
Variation. The colouration of the pleuron and metaleg is quite variable: darker specimens having katepisternum blacker on ventral side and darker annulus on metafemur, and lighter specimens with a yellow metaleg. The abdominal pattern is similar in all studied specimens, with the broad fasciae on terga 2 and 3 more or less visible. The wing colouration is also variable and some specimens with apical part hyaline. The wing is completely microtrichose, but a very few specimens have very small areas (not well defined) in the very basal part of the cell BM (less than 1/20 of the cell).

Geographical distribution
Species known from New Guinea Island, Sumbawa Island* and Philippines (Luzon)*.

Differential diagnosis
Species with yellow face, alula bare, narrower than costal cell, wing entirely microtrichose and infuscated, and without mesonotal fringe. The abdominal pattern is identical to another two species with tergum 4 entirely black, A. bicolor and A. tripartita, but differs by the wing microtrichia as stated in the key.
Original type locality Papua New Guinea: Paumomu (river), unknown coordinates (de Jong 2000). specimens are similar to Baccha sulica Austen, 1893. Again, he listed the differences with sulica and these were only about colouration.

Neotype locality
The type material of Baccha loriae, which belongs to the MSNG, was destroyed/lost in a fire at the HNHM during the 1956 uprising in Budapest (de Jong 2000; and confirmed by current personnel of both institutions: Maria Tavano, MSNG; and Zoltán Soltész and Eszter Ágnes Lazányi-Bacsó, HNHM). The second female from Bujacori was found at the MSNG and identified as Asiobaccha bicolor.
The colour variation mentioned by de Meijere (1908) is in the normal variation range of A. bicolor, and it might be possible that Baccha loriae is a junior synonym of A. bicolor. The problem is that there are three very closely related species with the same external appearance (see below) and the type of loriae is destroyed. Accordingly and in order to give a name to a taxon close to A. tripartita and A. bicolor, a neotype for Baccha loriae de Meijere, 1908 is here designated to fix and ensure the universal and consistent interpretation of the name.
Asiobaccha loriae belongs to a species group within Asiobaccha that lacks a mesonotal collar and has similar abdominal pattern, including A. bicolor, A. tripartita and A. loriae. This group might be a complex of more species with significant differences in the wing microtrichia pattern, or they might belong to a single, variable, widespread species. Male genitalia of the three recognised species are identical, as well as general external morphology and colouration. The variation occurs in the wing microtrichia, and the author has been able to separate the three taxa mentioned above. In the author's opinion, another source of characters, such as DNA, will be needed to solve this doubt, although the wing microtrichia pattern serves to separate well all three recognised species.
Female. Similar to male except normal sexual dimorphism and as follows: lunule black; frons yellow laterally on basal 1/2 with a medial, black vittae joining the black area on posterior 1/2, shiny on basal 1/2 and yellow pollinose on posterior 1/2 and ocellar triangle. The pollinose area on posterior 1/2 of the frons has a thin, medial shiny vitta (Figure 12e). Both female paratypes lack the alula, but this might be due to preservation conditions in author's opinion.

Geographical distribution
Sumatra and Malay Peninsula.

Etymology
The specific epithet is derived from the Latin maculosus denoting spotted, dappled (Brown 1956, p. 742). The name is to be treated as adjective.

Differential diagnosis
This species present a face entirely yellow, not pollinose, frons with a dark macula on lunule, alula very narrow, and the scutellum yellow with a medial, dark macula. This taxon is similar to A. tinctiventris, but it differs in the following characters: alula narrow (A. tinctiventris has the alula broader than costal cell), frons and face largely shiny, and yellow markings on tergum 3.

Remarks
The type material of Asiobaccha maculosa was identified as Baccha loriae Meijere most probably by Pieter H. van Doesburg (Senior). This conclusion by Herman de Jong and Ben Brugge (RMNH) was made after a handwriting comparison with the handwriting on labels of species described by van Doesburg. Originally a coleopterist, van Doesburg started to work on the Syrphidae during the Second World War. He identified remaining unsorted material in the Amsterdam Syrphidae collection, and it must have been in the early 1940s that the identification labels were attached (2014 e-mail from H. de Jong to author). The type material of A. maculosa does not match the original description of Baccha loriae. Meijere clearly stated that the scutellum was uniform in colour (de Meijere 1908, p. 319, key couplet 7) and the abdomen had no yellow markings (de Meijere 1908, p. 319, key couplet 8). The paratypes of A. maculosa, two females and a male, have no alula. After checking the male genitalia and all other external morphological characters, the author could not find any difference except the absence of the alula. Therefore, the author assumes the loss of the alula due to preservation conditions as this has occurred with the lectotype of A. virtuosa.
The Malayan specimen in the USNM was identified as Episyrphus 74-27 Thompson, in litt.

Variation.
The dark annulus of the metafemur is not well-defined in some specimens. The extension of the black posterior area on scutum is variable, as well as the extension of the posterior black fascia on terga 3 and 4.

Geographical distribution
Species known only from Sulawesi.

Etymology
This species is named after my wife, Marissa Sendra i Peiró, in her honour. This species is the most colourful, radiant and distinguished of Asiobaccha, just as Marissa is for my life.
The name is to be treated as a noun in the genitive case.

Differential diagnosis
Species with a narrow alula, without mesonotal fringe, tergum 4 with an anterior, broad yellow fascia and scutellum yellow. Asiobaccha marissae has unique characteristics, such as the abdominal colouration and the lobular expansions on each side at the antennal base. This species is similar to Asiobaccha notofasciata but the latter has a well-developed mesonotal fringe, alula broad and no modified antennal base. Asiobaccha marissae differs from other species without mesonotal fringe by the yellow fascia on tergum 4 and the antennal base expansions. Description Male: Head. Face with distinct round facial tubercle, yellow, white pollinose, yellow pilose except black pilose laterodorsally; gena yellow; lunule yellow, yellow also between antennal bases; frons protruded forward, black with anterior M-shaped yellow macula, black pilose, golden-brownish pollinose posteriorly, shiny black medially; vertical triangle narrow, isosceles, with the ocelli on the anterior half, black, black pilose; antenna yellow, black pilose; arista dark brown, bare; eye bare, holoptic; occiput black, grey-silver pollinose, yellowish-white pilose on ventral 2/3 and brown pilose on dorsal 1/3 ( Figure 7f).
Female. Similar to male except normal sexual dimorphism and as follows: frons black, with anterior yellow macula, white pilose, white pollinose except a thin shiny medial line. Pleuron more yellow, lighter; scutellum yellow. Abdominal tergum 1 yellow laterally, tergum 2 with basolateral maculae and medial maculae connected laterally with yellow lateral margins, tergum 5 with two yellow maculae on anterior margin.
Variation. Female from Mt. Garnet is a bit lighter, and it seems to be a teneral specimen.

Geographical distribution
Species known from New South Wales and Queensland (Australia).

Etymology
The specific epithet is derived from the Greek notos meaning south (Brown 1956, p. 731) and the Latin fasciatus meaning 'envelop with bands, swathe' (Brown 1956, p. 317), and it refers to Australia and the characteristic abdominal fasciae of this species. Species epithet is to be treated as adjective.

Differential diagnosis
This taxon has a broad alula, mostly bare, with a yellow face and a pale scutellum ( Figures  8e, 14a), with a well-defined mesonotal collar, and the metatarsus bicolourous (Figure 8a). This species has an infuscated wing, bare basomedially (including basal part of cell R), and terga 1 and 4 black (Figures 8a, 12c, 14a), characteristics that differentiate A. nubilipennis from A. virtuosa. Asiobaccha nubilipennis belongs to a species group with mesonotal fringe, which includes A. aea, A. virtuosa, A. doesburgi, A. notofasciata, A. aquila and A. bimaculata.
Morphologically, the most similar species to A. nubilipennis is A. bimaculata, also with terga 1 and 4 black and metatarsus bicolourous, but they can be identified using the characteristics in the key. Moreover, A. nubilipennis has tergum 3 black with a basomedial yellow fascia not reaching basal margin, a different abdominal pattern from A. bimaculata that has tergum 3 with two medial subtriangular yellow maculae pointing anteriorly. Variation. Species slightly variable, although its geographical distribution is the largest in this genus. Some specimens of A. nubilipennis from Sumatra have the cell R almost entirely microtrichose but with a basal, small bare area. The infuscation of the wing is very variable, from a medial, small brown area to a complete dark brown wing. The author has studied a female (JAPAN: Ryukyu, Iriomote Island, 1 July 1932; USNM) that has the yellow fascia on abdominal tergum 3 divided medially into two maculae.

Geographical distribution
Species with the widest geographical range in the genus. It is known from Sri Lanka, India, and Nepal* through China* to Japan, Myanmar*, Taiwan, Vietnam, Laos, Thailand, Malaysia and south to Indonesia (Sumatra, Java, Sulawesi). Knutson et al. (1975) listed this species from Nepal for the first time in the literature based on citations in older literature. There is only one taxon from Nepal, listed as Baccha sp. near maculata Walker, which might refer to A. nubilipennis, but this single female has the thorax, scutellum and pleura shining black; thus, it cannot be A. nubilipennis. This author has checked all the literature used by Knutson et al. (1975) and additional works, and has not found any citation of A. nubilipennis from Nepal. Consequently, the presence of A. nubilipennis in this country is questionable.

Remarks
Austen (1893) described this species from several male and female specimens collected by L.C. Yerbury in Sri Lanka. He stated that the typical specimens are a male collected on 28 June 1892 and a female collected on 25 May 1892. In the BMNH, there were two males, and the specimen collected on 28 June 1892 by Yerbury is designated here as the lectotype to fix and ensure the universal and consistent interpretation of the name. At the BMNH there was another female specimen collected by E.E. Green from Sri Lanka with the 'paralectotype' label. The present author does not consider it a paralectotype because Austen (1893) did not list this specimen among the studied material.

Differential diagnosis
Species with the face, the scutellum and the abdomen dark (Figure 8c), with bluish shine, and with a broad alula (Figure 8d, f). It is very similar to A. samoaensis, both with the metatarsi dark brown or black (Figure 8d), but they can be distinguished by the microtrichosity of the basal cells: A. praefica has the cell BM bare basally (also cell CuP sometimes), and A. samoaensis has the wing entirely microtrichose. Usually specimens of A. praefica show a pollinose abdominal pattern (black pollinose maculae on terga 2-4), that most specimens of A. samaoensis lack; but the pollinose pattern is variable and some A. praefica may not clearly show it.
Variation. Specimens from Fiji at CNC show a more microtrichose wing, but cell BM has a bare area basally. Nevertheless, this bare area is smaller (about 1/4) than the bare area in other specimens (about 1/2 basal cell BM).
[red; second and third lines handwritten]. This specimen is here designated as lectotype to fix and ensure the universal and consistent interpretation of the name. The other female syntype has been labelled as paralectotype. The three specimens collected in Vanuatu by L.E. Cheesman have a manuscript name provided by Frank M. Hull, Baccha praefica subsp. opacea. This name has been never published; thus, it is not available.
Female. Similar to male except for normal sexual dimorphism and as follows: frons black, shiny, white pollinose only lateroventrally; occiput entirely pale pilose.
Variation. Some specimens may have the face, under the white pollinose laterals, a yellow background. Lighter individuals have basal part of pro-and mesotibiae yellow and postalar callus light brown.

Geographical distribution
Species known only from Samoan Islands.

Etymology
The specific epithet is derived from the country's name where the species is found, Samoa, and the Latin suffix -ensis denoting place, locality, country, or belonging to, pertaining to (Brown 1956, p. 45, 303). Species epithet is to be treated as adjective.

Differential diagnosis
This taxon has the face, the scutellum and the abdomen dark, with purple shine, and it presents a broad alula. It is very similar to A. praefica, both with the metatarsi dark brown or black, but they can be distinguished by the microtrichosity of the basal cells: A. praefica has the cell BM bare basally, and A. samoaensis has the wing entirely microtrichose.

Differential diagnosis
Asiobaccha sauteri has no alula, the anal lobe is reduced, and the cell C microtrichose (Figure 9c, d). This species is distinguishable from other species by yellow markings on abdomen and by the absence of an alula.
Variation. Some specimens have two small yellow maculae on tergum 4 anterobasally without reaching any margin. Specimens collected in Philippines and Sulawesi are darker than the other studied individuals, with the face entirely black (see Figure 9f). At first, the author thought about describing a new species, but the variability of the dark areas in the face and pleuron as well as in the abdomen makes this option risky. These specimens have scutum and scutellum black and face black, except the female from Sulawesi that has black face and yellow scutellum.

Geographical distribution
Taiwan, Vietnam, Indonesia (Sulawesi) and Philippines (Luzon). Taiwan Remarks Kertész (1913) based his new species on several specimens, male and female individuals, from different localities of Taiwan: Takao (8 November 1907) [now known as Kaohsiung], Janano-Taiko (October 1908), Kosempo (20 January 1908, 21 March 1908, June 1908), Tainan (February 1909), Koshun (October 1908, March 1909 [now known as Hengchun], Fuhosho (July 1909) andSokotsu (May 1912). The author assumes that the Kertész's collection was deposited at the Hungarian Natural History Museum (HNHM) and that most of this material perished in a fire in 1956, as did most of the Syrphidae collection. This fact has been corroborated by HNHM personnel. Kertész (1913) Kertész, 1913// ZMAN type DIPT.1769. This male specimen is missing the entire abdomen, but the most important characteristic is that it has a very narrow, linear alula. This specimen keys out to another species in the present identification key, A. tripartita, but this male has alula microtrichose and linear, not bare and triangular as in A. tripartita. At this moment, the author cannot identify this syntype without doubt and prefers to leave this specimen without species name.

Type locality
There is another male, deposited at the USNM, studied and identified by Kertész (original handwriting on the identification label), which is not listed in the original description. Thus, it is not included in the type series, although it bears a 'typus' label.
Specimens from Philippines are darker than other studied specimens as mentioned above. The female from Sulawesi has a bit more different abdominal colouration, but this came out of a Malaise trap and it was dried out using the alcohol/xylene-amyl acetate method (van Achterberg et al. 2010). These specimens might represent a different species or just a local variation of A. sauteri.
Female. Similar to male except for normal sexual dimorphism and as follows: gena yellow, frons black, shiny, white pollinose only laterally, pale and dark pilose. Abdomen dark, black pollinose on apical 1/5 on tergum 2, and on apical 1/3-1/2 on terga 3 to 5; the area not covered by the black pollinosity is bluish grey, pale pollinose.
Variation. Face is variable between light brown to brown. Some specimens are lighter having scutellum yellowish and lateral margins of the scutum light brown; others have the scutellum dark brown. In some female specimens the abdominal area not covered by the black pollinosity is lighter without becoming yellow or orange. Thus, the abdomen is dark in general, but paler colouration might appear due to preservation/drying conditions.

Geographical distribution
Species known only from New Guinea.

Etymology
This species is named after all of my colleagues at the Systematic Entomology Laboratory, Agricultural Research Service, United States Department of Agriculture (SEL), and all my colleagues and friends at the Entomology Department of the USNM, Smithsonian Institution (SI). The name is a combination of letters (acronyms SEL + SI) and is to be treated as a noun in apposition.

Differential diagnosis
Asiobaccha selsi has no alula and a reduced anal lobe of the wing. This species is darker than other species without alula, with tergum 1 dark and most of the abdomen without clear pale markings. Asiobaccha selsi differs from other species without alula by having the wing cell C almost completely bare, microtrichose on apical 1/5 or less.  (Figure 10g).
Variation. The holotype has tergum 3 darker, and the paratype male misses the head.

Geographical distribution
Species known only from Solomon Islands.

Etymology
The specific epithet is derived from the Catalan taronja meaning orange. Species epithet is to be treated as adjective.

Differential diagnosis
This species is very distinct, mostly orange-yellow with terminal terga black, with a broad head and a narrow face, and very large male genitalia, unique among other species of this genus (Figure 13c, d). Asiobaccha taronja belongs to a species group with pale markings on abdomen, narrow alula, and without mesonotal fringe, which occur from Indonesia south and eastwards. This species has a short and robust abdominal pedicel (tergum 2) compared with the species group with mesonotal fringe (e.g. A. virtuosa and A. nubilipennis, among others) and it is very easy to distinguish from other species, such as A. marissae and A. bicolor, by the large male genitalia and the overall body colouration, especially the orange mesonotum.  Differential diagnosis Species with the face entirely yellow, densely yellow pollinose, and the frons with a medial dark macula on lunule, and very pollinose laterally and posteriorly (Figures 11e, 12f). The abdomen is very petiolate, with tergum 3 broadening considerably (Figure 11a, b). This species is similar to A. maculosa, but differs in the following characters: the alula is broad, broader than the costal cell; frons and face are densely pale pollinose; the ocellar triangle is shiny; the metatibia is mostly black, yellow only basally; and tergum 3 has yellow markings (a single medial, triangular yellow fascia that is not divided medially).
In the opinion of this author, this species might refer to the unpublished name of Baccha papuana Hull that appears in two specimens from Mafulu kept at the BMNH and CNC, although there is no information in the original labels about Tiracola.
After studying the work of , this citation may refer to a larva of a syrphid species parasiting a larva of Tiracola Moore, 1881 (Lepidoptera: Noctuidae) from Barevaturu N.P. in Papua New Guinea. However, there is no species of Asiobaccha or Baccha that parasitises butterfly larvae. Consequently, this record by  may not refer to a species of Baccha, Allobaccha or Asiobaccha, or, on the other hand, it might indicate that the larva of Baccha was preying on the Tiracola larva and the adult emerged from a puparium.

Geographical distribution
Kai Islands, Misool Island, New Guinea Island, New Ireland Island and Woodlark Island.

Geographical distribution
Malay Peninsula, Sumatra and Borneo.

Type locality
Malaysia: Pahang, Cameron's Highlands, Rhododendron Hill, 04°29ʹN, 101°22ʹE. 11. Abdominal tergum 1 black or brownish, sometimes yellowish on lateral margins ( Figure 4a); tergum 2 black with two pairs of yellow maculae: one basally, which may join medially, and another medially; tergum 3 with two triangular maculae or with a broad yellow fascia not reaching anterior margin (Figures 4a, 8a)............. 14 - Abdominal tergum 1 yellow with or without narrow dark fascia on posterior margin ( Figure 12a); tergum 2 yellowish, brownish posteriorly, with a dorsomedial brownish macula; tergum 3 with broad yellow fasciate maculae reaching anterior margin (Figures 5c, d, 7c) 12. Cell R entirely microtrichose posterior to spurious vein (Figure 14b). Tergum 4 with two subtriangular/rectangular yellow maculae, isolated from anterior margin (Figure 12a, b) Burt for the fantastic drawings of male genitalia and wing microtrichia patterns used in Figures  13 and 14. I am very grateful to Jeff Skevington and Andrew Young for all the shared information about Australian specimens: barcodes, metadata, specimens, geographic information and images. I sincerely thank F. Christian Thompson for comments, support, guidance and best-practice advice during so many years, as well as for sharing his knowledge on syrphid flies and for coauthorship in some of the new species reported here. I also thank Jeff Skevington, Martin Hauser and two anonymous reviewers for the very helpful comments and suggestions.

Disclosure statement
No potential conflict of interest was reported by the author.