A new species of Ischiodon Sack ( Diptera , Syrphidae ) from Madagascar

The flower fly genus Ischiodon Sack (Diptera, Syrphidae) is revised and a new species, Ischiodon astales sp. n., is described from Madagascar. Additionally, a lectotype for Ischiodon aegyptius is designated and the first records of Ischiodon scutellaris for the Arabian Peninsula are reported. Diagnoses, illustrations, synonymies and distributional data are given for all described species, as well as an identification key to


Introduction
The genus Ischiodon Sack, 1913 (Diptera, Syrphidae) is a small, but very characteristic genus, with a very broad distribution and a taxonomic history full of confusion and synonyms (Vockeroth 1969).The genus occurs in southern Europe, the Mediterranean basin, throughout all of the African continent, eastwards to India, China, Japan, southeast Asia, Australia and some Pacific islands (Huang and Cheng 2012, Thompson 2013, Speight 2017).Ischiodon species have been originally described in eight different genera, a fact that may indicate the morphological resemblance of these species with other syrphid taxa and the broad genus concepts of previous authors: i.e.Musca Linnaeus, 1758, Syrphus Fabricius, 1775, Scaeva Fabricius, 1805, Sphaerophoria Le Peletier & Serville, 1828, Xanthogramma Schiner, 1860, Epistrophe Walker, 1852, Melithreptus Loew, 1840 (a junior primary homonym of Sphaerophoria), and Ischiodon (Thompson 2013).On the other hand, a junior synonym of Sphaerophoria rueppellii (Wiedemann, 1830) was described as Ischiodon libycum Nayar, 1978.The confusion of Ischiodon as a valid genus is due to its superficial morphological resemblance with the genus Simosyrphus Bigot, 1882.This confusion started when Bezzi (1912:72) synonymised Syrphus grandicornis Macquart, 1842 (now Simosyrphus grandicornis) under Ischiodon scutellaris (Fabricius, 1805).Species of both genera have been previously placed under one another several times (Mengual 2015, see below under each species), despite some important differences in the male genitalia (Vockeroth 1969).The generic key by Vockeroth (1969) can be used to identify both genera.A synonymy of both genera was proposed by Láska et al. (2006) based on larval and pupal morphology, supported by a molecular study of a very limited taxon sampling using only part of the gene cytochrome c oxidase subunit 1 (COI).More recently, Mengual et al. (2018) resolved both genera as related to Scaeva but the genus Pseudodoros as sister group of Ischiodon; thus, current evidence supports the generic rank of Ischiodon and Simosyrphus.
Ischiodon comprises three species with quite distinct distributions: I. feae (Bezzi, 1912) is endemic of the Cape Verde Islands, I. aegyptius (Wiedemann, 1830) is mainly present in Africa and southern Europe and I. scutellaris (Fabricius, 1805) occurs in the Oriental and Australasian Regions.Larvae of I. aegyptius and I. scutellaris have been reported feeding on aphids (Hemiptera, Aphididae) mostly, but there are a few records on thrips (Thysanoptera), whiteflies (Hemiptera, Aleyrodidae) and caterpillars (Lepidoptera) (Rojo et al. 2003).
The aim of this study is to revise the genus Ischiodon and describe a new species from Madagascar, as well as to provide an identification key for all known species of this genus.In addition, a lectotype is designated for Syrphus aegyptius Wiedemann, 1830 and the first records of I. scutellaris from the UAE are reported.

Material and methods
Differential diagnoses, synonymies and distributions are given for all studied species.The new species is described in full, with terminology following Thompson (1999) and Cumming and Wood (2009).The abbreviations used for collections follow the standard of the Systema Dipterorum (Thompson 2013) and their equivalents are given below:

CAS
California Academy of Sciences, San Francisco, USA.

CSCA
California State Collection of Arthropods, Sacramento, USA.

MZH
Finnish Museum of Natural History, Helsinki, Finland.
In the description of type labels, the contents of each label are enclosed within double quotation marks (" "), italics denote handwriting and the individual lines of data are separated by a double forward slash (//).At the end of each record, between square brackets ([ ]) and separated by a comma, the number of specimens and sex, the holding institution and the unique identifier or number are given.
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).Simple-Mappr (Shorthouse 2010) was used to create Figure 4. 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.

Genus Ischiodon Sack, 1913
Type-species.Ischiodon trochanterica Sack, 1913, by monotypy; junior synonym of Scaeva scutellaris Fabricius, 1805.Differential diagnosis (adapted from Vockeroth 1969).Small to medium-sized, rather slender species with yellow-margined mesonotum, broad yellow fasciae on abdomen and very large and prominent male genitalia.Face yellow, with or without medial black vitta; eye bare; basoflagellomere large, twice as long as broad, tapering slightly to an acutely rounded apex.Mesonotum shining black with broad, well-defined, pale to bright yellow lateral vitta extending to postalar callus.Scutellum yellow, usually obscurely brownish on disc.Pleuron mostly shining black, except posterior anepisternum yellow on posterior half and katepisternum with a dorsal yellow macula.Dorsal and ventral katepisternal pile patches broadly separated posteriorly.Metasternum bare.Wing with microtrichia greatly reduced, absent from most of basal half and elsewhere very sparse and irregularly scattered.Abdomen elongate, parallel-sided or very narrowly oval, rather flattened, with a strong margin from middle of tergite 2 to the end of tergite 5. Tergite 2 with a pair of separate or narrowly confluent pale maculae; tergites 3 and 4 each with a rather broad, slightly arcuate yellow fascia separated from the base of each tergite.Very often, the black abdominal areas become reddish or yellow towards the abdominal apex, so the pattern is indistinct.
In males of I. aegyptius and I. scutellaris, the ventral surface of the metatrochanter has a slender or moderately stout, cylindrical, apically acute process (calcar) of varying length.In males of I. aegyptius and I. feae, the inner (mesial) claw of the protarsus has a dorsal preapical projection, or flange, which gives the claw a truncated appearance (Fig. 5F).
Several authors (including the present author) used the species epithet of Ischiodon aegyptium in neuter form.Ischidon must be treated as a masculine gender and all species names must follow this gender except nouns in apposition.Thus, the correct species epithet is Ischiodon aegyptius.

Differential diagnosis.
Very common species in the Afrotropical region with yellow markings on abdomen reaching the lateral margins (Fig. 1A, C).Males of I. aegyptius have metatrochanters with a long calcar (Fig. 1E) (short calcar in I. scutellaris) and the claws of the fore leg are asymmetrical (as in Fig. 5F) (males of I. feae also have asymmetrical claws but they do not have a calcar on the metatrochanters).The male genitalia are quite unique with a trilobed surstyli (Fig. 1F).Females are very difficult to distinguish from females of I. scutellaris as the pattern of tergite 2, very often used to distinguish them (Sack 1932, Huang and Cheng 2012, Speight and Sarthou 2017), is variable.At this moment, conspecific males, DNA barcodes and/or collecting locality may help to distinguish them.Geographical distribution.African continent and archipelagos, southern Europe, Israel and Arabian Peninsula.
Type-locality.Wiedemann (1830) studied an unknown number of specimens from Egypt and Nubia (currently divided into Egypt and Sudan).All the syntypes present in the ZMF collection, collected by Rüppell with original handwritten labels, were collected from Abyssinia, a historical region in northern Ethiopia and southern Eritrea, although sometimes east Sudan is also considered part of this kingdom.Thus, the typelocality is here restricted to Eritrea and Ethiopia based on the lectotype designation.
Material examined.More than 300 specimens from UAE, Israel, Cyprus, Morocco, Canary Islands, Madagascar, Kenya, The Gambia, Central African Republic, Zimbabwe and South Africa.
Some authors (Huang et al. 1996, Huang andCheng 2012) reported specimens identified as I. aegyptius from China, with a complete overlapping distribution inside this country with I. scutellaris (see Huang and Cheng 2012).In the author's opinion, only I. scutellaris occurs in China and these specimens are misidentifications when the pattern of the tergite 2 is used in females for identification.These works (Huang et al. 1996, Huang andCheng 2012) do not specify if there are males of I. aegyptius amongst the studied material, which could be used to corroborate the author's opinion.
Ischiodon astales sp.n. http://zoobank.org/B32ED255-02F5-4465-8CBC-7B7EA64404CCFigures 2, 3A-D, 4 Differential diagnosis.Females and males of this new species do not have a calcar on the metatrochanter and they are easy to distinguish from other species since the two broad, yellow maculae on tergite 2 do not reach the lateral margins (Figs 2A, C, 3A, C).Moreover, males of I. astales sp.n. have symmetrical claws on the fore leg, the same as males of I. scutellaris.
Abdomen (Fig. 2A, C): Parallel-sided, with lateral margin from apical 1/2 of tergite 2 to tergite 5. Tergite 1 black, except yellow on lateral margins, yellow pilose; tergite 2 black, paler medially on posterior margin, with two large, rounded yellow maculae that do not reach lateral margins, yellow pilose, with short black pile on posterior margin; tergite 3 black on basal 1/2 becoming orange or brownish on posterior 1/2, with a medial yellow fascia that does not reach the lateral margins, with scattered, short, black pile; tergite 4 brownish-orange with a medial yellow fascia, black pilose except on the yellow fascia; tergite 5 brownish-orange, black pilose.Sternite 1 yellow; sternite 2 yellow with a medial, round, black macula; sterna 3 and 4 yellow becoming darker (brownish orange) towards genitalia; all sterna with yellow pile.Male genitalia: large, brownish-orange, as in Fig. 2E, F.
Female: Similar to male except for normal sexual dimorphism and as follows: frons black on dorsal 1/3, yellow on ventral 2/3 with a variable medial brownish orange vitta.
Variation: Due to the small number of specimens, one must expect variability in the coloration of the abdomen, legs and female frons, as in other Ischiodon species.
Etymology.The specific epithet is derived from the Greek astales meaning unarmed, unclad (Brown 1956: 122).Species epithet is to be treated as an adjective.
Material examined.Type material.Holotype, male, pinned with genitalia in microvial, deposited in the CAS and labelled: "MADAGASCAR, Tulear // Province, Mikea Forest, // NW of Manombo, el 30 m, // 17 -27 July 2003" "22°54.22'S,43°28.53'E// coll: M. Irwin, R. Harin'Hala // California Acad of Sciencies // malaise trap -in deciduous //  Remarks.All specimens of this new species were collected using Malaise traps in different habitats.The male holotype was collected in a deciduous dry forest, while females CASENT 2210150 and CASENT 2210121 were collected in dry spiny forests and the female CASENT 2210162 in a gallery forest.On the other hand, the female ZFMK-DIP-00026782 was collected at a relative high altitude compared with the other specimens.

Differential diagnosis.
Very widespread species with yellow abdominal marking reaching lateral margins (Fig. 6A, C).Males have the metatrochanters with a short calcar (Fig. 6E) and the claws in all legs are symmetrical.The pattern of tergite 2 in females is variable and cannot always be relied on to distinguish the females of I. scutellaris from those of I. aegyptius.
Geographical distribution.From Greece, eastwards to Caucasus, Kazakhstan, Iran, Arabian Peninsula south to Indomalayan region, China, Japan, Taiwan and Australasian and Oceanian regions except Hawaii.I. scutellaris has not been reported from Korea (Han and Choi 2001).Material examined.More than 150 specimens from Greece, UAE, Kazakhstan, Iran, Nepal, Indonesia, Thailand, Taiwan, Australia, New Caledonia and French Polynesia.The syntypes of Scaeva scutellaris Fabricius, 1805 were not studied for the present study.

Discussion
A new species of Ischiodon is described from the southern regions of Madagascar.It should be noted that the male holotype and the four female paratypes of I. astales sp.n. were found amongst more than 200 specimens of Ischiodon aegyptius collected over several years (2002)(2003)(2004)(2005)(2006)(2007)(2008) using Malaise traps (specimens deposited in the CAS).This might indicate the scarcity of this new species in nature, but the fact that I. astales has been collected in several habitats and at different elevations might indicate the opposite, i.e. the new species is more common than the number of specimens studied suggests.
Ischiodon scutellaris has reached the Mediterranean Basin and it is present in Greece, Crimea Peninsula and Turkey and might eventually reach northern areas of the Balkan Peninsula.In contrast, the species present in the Iberian Peninsula, Macaronesia, Italy, northern parts of the African continent, Cyprus and Israel is I. aegyptius.It seems that there is an overlapping area of these two species including the southern region of Turkey and Iran, where both species have been reported (Kazerani et al. 2013, Naderloo et al. 2013, Sarıbıyık 2014, Khosravian et al. 2015) and now also in the UAE.One is biased to think that the specimens of I. scutellaris collected in the UAE arrived from across the Persian Gulf or the Gulf of Oman, as there are no records of I. scutellaris from Iraq, Kuwait or Saudi Arabia.On the other hand, I. scutellaris might be present in these countries, but the lack of data makes any assumption difficult to corroborate as the syrphid fauna from these countries is poorly known.Speight (2017) affirms that I. aegyptius is possibly a non-resident species in Europe, but it repeatedly establishes temporary populations that may, or may not, survive from one year to the next in Europe.Contrary to Speight (2017), the author believes that I. aegyptius and I. scutellaris are both resident species in Europe based on the number of continuous records and new evidence, as the habitats in the Mediterranean Basin between countries are not so different.