The family Stratiomyidae in Egypt and Saudi Arabia (Diptera: Stratiomyoidea)

Abstract Background This study systematically catalogues all known taxa of the family Stratiomyidae in Egypt and Saudi Arabia. It is one in a series of planned studies aiming to catalogue the whole order in both countries. New information Twenty species, belonging to seven genera and three subfamilies (Pachygastrinae, Stratiomyinae and Nemotelinae), are treated. One of these genera, Oplodontha and two species, Oplodontha pulchriceps Loew and Oxycera turcica Üstüner & Hasbenli, are recorded herein for the first time from Saudi Arabia. A lectotype for Nemotelus matrouhensis Mohammad et al., 2009 is designated. An updated classification, synonymies, type localities, world and local distributions, dates of collection and some coloured photographs are provided.


Introduction
The Stratiomyidae is a lower brachycerous Dipteran family, including more than 2650 species classified in 375 genera and 12 subfamilies worldwide (Woodley 2001). Flies of the family Stratiomyidae, commonly known as soldier-flies, are small to large, ranging from 2 to 28 mm in length, highly varied in shape and colouration, with wings hyaline to variously patterned or infuscated and some species likely mimic wasps and bees in their flight and body colour (Hauser 2008, Hauser et al. 2017b). These flies can be easily distinguished as adults by the following characters: radial veins grouped together anteriorly, ending before tip of the wing; costal vein (C) usually ending well before wing apex and discal cell (d) short, usually forming distinct short, often squarish cell at middle of the wing (Marshall et al. 2017).
Adult soldier-flies can be found sitting on foliage in sunny locations in damp forest habitats, near water or boggy areas and some flies can be found frequenting flowers, particularly those of the subfamily Stratiomyinae and some of the subfamily Clitellariinae (James 1981, Hauser et al. 2017b).
Immature stages of soldier-flies can be found in a variety of habitats. Larvae of the subfamilies Beridinae, Clitellariinae and Sarginae, which have not been represented in Egypt or Saudi Arabia, are usually associated with decaying organic matter, such as leaf litter and rotting fruits. However, larvae of the subfamilies Nemotelinae and Stratiomyinae are aquatic, occurring in slow moving or standing water in rivers, ponds, seepage areas and other transient water sources, with those of the genus Nemotelus Geoffroy, 1762 being remarkably tolerant to high levels of salinity. Larvae of the subfamily Pachygastrinae can be found under the bark of fallen trees (Rozkošný 1983, Hauser 2008, Hauser et al. 2017b.
Of the 12 subfamilies, seven are recorded in the Palaearctic Region with about 430 species (Woodley 2001). Of these, only three subfamilies (Pachygastrinae, Stratiomyinae and Nemotelinae) have been represented in Saudi Arabia and/or Egypt by seven genera comprising 20 species. One of these genera, Oplodontha and two species, Oxycera turcica Üstüner & Hasbenli and Oplodontha pulchriceps Loew, are recorded herein for the first time from Saudi Arabia. This is not surprising as no previous faunistic or systematic studies on the Stratiomyidae have been carried out in Saudi Arabia and only two species have been recorded from Saudi Arabia amidst two comprehensive checklists of the Saudi Arabian Diptera:  [Aspidacantha atra Kertesz] and Abu-Zoherah et al. (1993) [Stratiomys deserticolor Lindner]. We think the overall number of Saudi Arabian taxa treated in the present study is still low and does not represent the real fauna of Stratiomyidae in this country and an extensive faunistic and systematic study on the Saudi Arabian Stratiomyidae is required. On the other hand, some previous studies have been carried out in Egypt to list the Stratiomyidae species (Steyskal and El-Bialy 1967) or to study the fauna and/or taxonomy of the family (Lindner 1930, Badrawy 2006), in addition to some miscellaneous studies which described some new species from Egypt (Olivier 1811, Becker 1902, Wiedemann 1830, Lindner 1925, Lindner 1930, Lindner 1937, Lindner 1974. Egypt and Saudi Arabia are two neighbouring countries in the Middle East, separated by the Gulf of Aqaba and the Red Sea (Fig. 1). Egypt is a transcontinental country as its majority is located in the north-eastern corner of Africa, while its north-eastern extremity, Sinai Peninsula, is located in the south-western corner of Asia. On the other hand, Saudi Arabia is wholly located in the south-western corner of Asia. Both Egypt and Saudi Arabia are biogeographically located at the junction of the Palaearctic and the Afrotropical Regions. The faunal affiliation of the two countries is mainly Palaearctic. Exceptions are Gebel Elba, the south-eastern triangle of Egypt and the southwestern part of Saudi Arabia, south to the Tropic of Cancer, which are considered as having an Afrotropical faunal affiliation (Wallace 1876, Hölzel 1998, El-Hawagry and Gilbert 2014).
This study is one in a series of taxonomic studies on different Egyptian and Saudi Arabian dipteran taxa aiming to catalogue the whole order Diptera in the two countries (EL-     2017) reported this species as Sternobrithes sp. and further research indicated that this is an undescribed species (Fig. 3). As we do not have a male specimen available, we are not yet describing this species here. According the generic key in Hauser et al. (2017b), the difference between Argyrobrithes and Sternobrithes is the colour of the last antennal segment, but further studies indicate that Argyrobrithes is characterised by the dichoptic male eyes and a very long last antennal segment. The two genera are widely distributed through Africa and the Oriental Region and a more thorough revision is needed to clarify the limits of the genera and which species should be included in each genus. Material of this undescribed species are known from Yemen and Kenya.     Local distribution and dates of collection (Fig. 8)   Notes:  published this species and inaccurately cited 13 males and 8 females as "holotype". They did not explicitly select a single specimen as holotype, so all cited specimens are considered as syntypes and a lectotype should be designated. As the illustration of the male genitalia was made from an intact specimen and did not show all the important structures, we are providing an illustration of dissected genitalia (Fig. 12) and a habitus photograph of the specimen (Fig. 13). When one of us (MH) requested a specimen, we were told that this would be a paratype, but because the specimen had no identification or type label at all, a red label was generated and attached to this specimen. This label reads: Paratype ♂/ Nemotelus   Distribution map of Nemotelus niloticus Olivier and Nemotelus notatus Zetterstedt.

Local distribution and dates of collection
The family Stratiomyidae in Egypt and Saudi Arabia (Diptera: Stratiomyoidea)