Abstract
Catalogue and distribution data are presented for the six Diopsidae species known to occur in the Arabian Peninsula: Sphyracephala beccarii, Chaetodiopsis meigenii, Diasemopsis aethiopica, Diopsis arabica, Diopsis mayae and Diopsis sp. (ichneumonea species group). The biogeographical aspects of their distribution are discussed. Records of Diopsis apicalis and Diopsis collaris are removed from the list for Arabia as these were based on misidentifications. Synonymies involving Diasemopsis aethiopica and Diasemopsis varians are discussed. Only one out of four specimens in the D. elegantula type series proved conspecific with D. aethiopica. The synonymy of D. aethiopica and D. varians is rejected. A lectotype for Diasemopsis elegantula is now designated. D. elegantula is proposed as junior synonym of D. varians. A fly cluster of more than 80,000 Sphyracephala beccarii, observed in Oman, is described. The occurrence of cluster formations in the Diopsidae is reviewed, while a possible explanation is indicated.
Introduction
Westwood (1837b) described Diopsis arabica as the first stalk-eyed fly from the Arabian Peninsula. As type locality only “in Arabiâ desertâ” was given. Hennig (1941), in a contribution to “Die Fliegen der palaearktischen Region”, gave a partial redescription of D. arabica based on the type. Hennig indicated that it was not certain whether the type was collected in the Palaearctic or the Ethiopian part of Arabia. He was anyway of the opinion that it did not concern a typical representative of the Palaearctic fauna, but, at most, a species which had penetrated from the Ethiopian Region. The type now appears to be lost (Rohlfien & Ewald 1970). In the last world catalogue for Diopsidae, Steyskal (1972) only referred to Westwood and Hennig as far as Diopsidae in Arabia was concerned. Feijen (1989) recorded Sphyracephala beccarii (Rondani) and Chaetodiopsis meigenii (Westwood) for the Arabian Peninsula. Feijen mentioned the occurrence of seven Diopsidae species for this peninsula, but one of these later turned out to be based on a wrong geographic interpretation of a label.
In the past ten years, five papers were published dealing with the Diopsidae fauna of Arabia. In the first of these papers, Dawah & Abdullah (2008) recorded three Diopsidae species from south-western Saudi Arabia: “Diopsis collaris”, “Diopsis apicalis” and Sphyracephala beccarii. In the second one, Hauser et al. (2011) discussed the occurrence of Sphyracephala beccarii in the United Arab Emirates. They also gave records for the same species from Oman and Yemen. In the third paper, El-Hawagry et al. (2013) listed “Diopsis apicalis” and Sphyracephala beccarii for Al-Baha Province, Saudi Arabia. In El-Hawagry et al. (2015) “Diopsis collaris” was added to the list for Al-Baha Province, Saudi Arabia, while El-Hawagry et al. (2016) added more records for “Diopsis apicalis” and Sphyracephala beccarii.
We present here an annotated catalogue and a key to the six species presently recognized as occurring in Arabia. As the border between the Palaearctic Region and the Ethiopian Region in the Arabian Peninsula is formed by a somewhat indeterminate line, the biogeographical implication of the Diopsidae records will be discussed briefly. In Diopsidae, clustering was only known in the genus Sphyracephala. Feijen (1989) briefly reviewed the scarce records for this phenomenon in stalk-eyed flies. A recent observation of clustering in Oman is described. A review is presented for clustering in the Diopsidae while a possible explanation will be indicated.
Museum codens used
Annotated catalogue of Diopsidae in the Arabian Peninsula
Sphyracephala beccarii (Rondani)
Diopsis beccarii Rondani, 1873: 289 – type series from Eritrea, Sciotel, Bogos, 15°35’N 38°20’E, lectotype and part of large type series in MCSN, paralectotypes in many other museums.
Distribution maps of Diopsidae species in the Arabian Peninsula. – 1, Sphyracephala beccarii (also showing type locality in Eritrea); 2, Chaetodiopsis meigenii and Diasemopsis aethiopica (also showing type locality in Eritrea); 3, Diopsis mayae; 4, Diopsis arabica and Diopsis sp.
Citation: Tijdschrift voor Entomologie 160, 2 (2017) ; 10.1163/22119434-00002065
Sphyracephala beccarii, Osten Sacken 1882: 235. Ref.: Steyskal 1972, Feijen 1989, Hauser et al. 2011.
Diopsis africana Karsch, 1888: 380 – holotype from Tanzania, Bondei, ~5°00’S 39°00’E, in ZMHB but lost (see Rohlfien & Ewald, 1970). Ref.: Curran 1928, Séguy 1949, Collart 1954, Steyskal 1972, Cogan & Shillito 1980.
Distribution. Algeria, all contiguous Sub-Saharan African countries, Madagascar, Arabian Peninsula.
Arabian records. Oman, 7♀, 3♂, Wadi Siya, 23°12’N 58°41’E, 400 m, 10.iv.1980, B.R. Pitkin (BMNH); >80,000 specimens, Wadi Darbat, 17°6’58”N 54°27’18”E, 206 m, 10.xi.2014, R. Martin, M. Kühn, T. Wulf (observation & photographs); 2♀, 1♂, Ain Razat, 17°7’44"N 54°14’11”E, 200 m,13.ii.1989, M.J. Ebejer (Hauser et al. 2011) (NMWC); 2♀, Dhofar, Ain Sahwoot, 9.xi.1992, J.C. Deeming (Hauser et al. 2011) (NMWC); 2♀, 2♂, Dhofar, Ain Jarziz, 17°06’N 54°05’E, 197 m,11.xi.1992, J.C. Deeming (Hauser et al. 2011) (NMWC); 1♂, Dhofar, Ain Hamran, 17°6’4”N 54°16’37”E, 1.xi.1988, M.J. Ebejer (Hauser et al.2011) (NMWC); 1♂, Dhofar, Hajayf, 17°17’N 54°3’E, 12.x.1990, J.C. Deeming (Hauser et al. 2011) (NMWC); 1♀, Zufar, near Ayn Razat, 17°7’44”N 54°14’11”E, 200 m, 24.v.2012, Moayed Bahajjaj (photographic record, Flickr); Ayn Razat, 17°7’44”N 54°14’11”E, 200 m, 28.vi.2012, Moayed Bahajjaj (photographic record, Flickr); Ain Garziz, Zufar, 17°6’N 54°5’E, 197 m, 7.iii.2012, Faisal Salim (photographic record, Flickr); Saudi Arabia, 2♀, 2♂, Wadi Maharish, 21°21.5’N 40°13’E, 1000 m,13.i.1983, W. Büttiker (RMNH); 20♀, 28♂, Maraba, Asir, 17°54’N 42°23’E, 80 m (or 350 m?), 2004–2005 (Dawah & Abdullah 2008) (NMWC, NHMCSA); Al-Mekhwa, 19°46’14”N 41°26’3”E, 350 m, xii–ii.2008–2012 (El-Hawagry et al., 2013) (KSMA); Dhee Ain, 19°33’16”N 41°15’46”E, 155 m, ii–v.2008–2012 (El-Hawagry et al., 2013) (KSMA); Jabal Shada al-A’la Nature Reserve, 19°51’46”N 41°18’5”E 2.vi.2014, 19°50’20–43”N 41°18’16–41”E 3.vi.2014, 19°50’43”N 41°18’16”E 27.i.2015, 19°50’35”N 41°18’42”E 5.v.2015, 19°51’46”N 41°18’5”E, 15.xi.2015 (El-Hawagry et al., 2016) (KSMA); Yemen, 12♀, 14♂, Wadi Dareija, SW of Dhala, W. Aden Prot., 13°40’45”N 44°42’7”E, 4500’, 6–9.xi.1937, H. Scott & E.B. Britton; 1♀, Al-Lahima, 15°24’N 43°32’E, 1200 m,16.x–31.xii.2000, A. van Harten & A.M. Hager (Hauser et al. 2011) (NMWC); 1♀, Suq Bani Mansour, 15°6’N 43°50’E, 1500 m, 28.viii–26.ix.2001, A. van Harten (Hauser et al. 2011) (NMWC); 1♀, Ar-Rujum, 15°27’28”N 43°38’6”E, 1989 m, 16.x.2000, A. van Harten & A.M. Hager (Hauser et al. 2011) (NMWC); 1♀, 1♂, 12 km NW of Manakhah, 15°6’N 43°43’E, 1500 m, 21.viii.2001, A. van Harten (Hauser et al. 2011) (NMWC); 1♀, 12 km NW of Manakhah, 15°6’N 43°43’E, 1500 m, 5.v–17.vi.2002, A. van Harten (Hauser et al. 2011) (NMWC); United Arab Emirates, 21♀, 26♂, Wadi Hayl, 25°04.83’N 56°13.53’E, 240 m, 15.iii.2008, M. Hauser, J-H. Stuke; 1♀, Wadi W Mirba, 25°16.22’N 56°16.68’E, 260 m, 13.iii.2008, J.-H. Stuke; 1♂, Wadi Shawkah, 25°6’N, 56°2’E, 309 m, 20–26.iii.2007, F. Menzel. Distribution records are mapped in Fig. 1, which also shows the type locality.
Chaetodiopsis meigenii (Westwood)
Diopsis meigenii Westwood, 1837b: 548 (as Miegenii) – in Guineâ Africæ, type series (1♀, 1♂) in OXUM. Ref.: Eggers 1925.
Diopsis subfasciata Macquart, 1843: 395 – erroneously described from Java, Indonesia, holotype in MNHNP (fragment). Ref.: Feijen 1978.
Diopsis leucochira Bezzi, 1908a: 387 – type series from DR Congo & South Africa, in ISNB. Ref.: Feijen 1978, Feijen 1989.
Not Diopsis breviseta Bezzi, 1908b:167 – Eritrea, Massaua, Abd el Kader, 15°37’26”N 39°28’25”E. Ref.: Lindner 1962, Feijen 1978, Cogan & Shillito 1980, Feijen 1989, Carr et al. 2006.
Diasemopsis meigenii, Brunetti 1926a: 173. Ref.: Cogan & Shillito 1980, Carr et al. 2006.
Chaetodiopsis meigenii, Séguy 1955: 1108. Ref.: Steyskal 1972, Feijen 1989.
Distribution. All contiguous Sub-Saharan African countries, Arabian Peninsula.
Arabian records. Oman, Wadi Darbat, 17°6’58”N 54°27’18”E, 206 m, 10.xi.2014, R. Martin, M. Kühn & T. Wulf (observation & photographs); 1♀, Kelen, Zufar, 17°5’16”N 54°19’10”E, 120 m, 28.ix.2012, Moayed Bahajjaj (photographic record, Flickr); Saudi-Arabia, 1♀, Fifa (Fayfa?), nr. Gizan, 17°15’N 43°6’E, 1240 m, 27–31.iii.1983, C. Holzschuh (NHMB); Yemen, 16♀, 12♂, Usaifira, 1 mile n. of Ta’izz, 13°38’N 44°1’E, 4500 ft, 13.xii.1937, H. Scott & E.B. Britton (BMNH); 1♂, Ta’izz, 13°38’N 44°1’E, i.1951 (NHMB). Distribution records are mapped in Fig. 2.
Diasemopsis aethiopica (Rondani)
Diopsis aethiopica Rondani, 1873: 289 – holotype from Eritrea, Sciotel, Bogos, 15°35’N, 38°20’E, in MCSN Ref.: Guiglia 1957.
Diasemopsis veliventris Hendel, 1923: 41 – Kenya, Wa-Kikuyu, Tchania (Chania) River and Wa-Taita, Bura, in NHMW. Ref.: Curran 1931, van Bruggen 1961, Steyskal 1972.
Not Diasemopsis varians Eggers, 1916: 12, 27 – Kenya, River Lumi (type series not traced). Ref.: Curran 1931, van Bruggen 1961, Steyskal 1972.
Not Diasemopsis elegantula Brunetti, 1926b: 82 – type series consisting of 3 “cotypes” from DR Congo (MRAC) and 1 “syntype” from Durban, South Africa (BMNH). Three specimens of the type series, including the now newly designated lectotype, are conspecific with D. varians, while only one paralectotype from DR Congo is conspecific with D. aethiopica. Ref.: Curran 1931, van Bruggen 1961, Steyskal 1972.
Distribution. All contiguous Sub-Saharan African countries, Arabian Peninsula.
Arabian record. 1♀, Yemen, Wadi Tiban, NW of Jebel Jihaf, 13°47’N 44°34’E, 3800 ft, 21.x.1937, H. Scott & E.B. Britton. Distribution record is mapped in Fig. 2, which also shows the type locality.
Remarks. Diasemopsis aethiopica and D. varians are two of the most common and abundant Diasemopsis with a wide distribution in the Afrotropical region. They often occur together. Although closely related, they can easily be separated. Diasemopsis varians is smaller, darker and a bit more hairy. The first sternum is grey in D. aethiopica and black in D. varians. The pollinose spots on the abdomen are angular in D. varians and rounded in D. aethiopica. In D. aethiopica the wing has a vague central wing spot (Fig. 13), while in D. varians the wing is apically slightly infuscated. Being such common species, it is not surprising that they have several times been described as new species. Curran (1931) considered D. aethiopica “A variable species in the female sex”. He indicated a colour difference between males and females: “Male – abdomen rarely reddish on the fourth segment, otherwise like the female”. However, reddish-brown fourth sterna and especially third sterna occur in both sexes. Curran indicated D. varians, D. veliventris and D. elegantula as synonyms of D. aethiopica. The main illustration and the description by Eggers (1916) clearly cover D. varians as now distinguished from D. aethiopica. Eggers considered D. varians as rather variable and related to D. aethiopica. From the description and the two additional abdomens illustrated, it is clear that Eggers’ type series of six specimens must have been mixed, but it did not contain a D. aethiopica. Whether the type series still exists is not clear.
Van Bruggen (1961) thought it convenient to accept the redescription given by Curran (1931), but did not wholly agree with his synonymy. He considered D. elegantula Brunetti as certainly not synonymous with Rondani’s species. Examination of the three “cotypes” of D. elegantula in MRAC revealed that two are conspecific with D. varians while one is conspecific with D. aethiopica. The “syntype” in BMNH is rather incomplete (no abdomen) and is likely to be also a D. varians. One of the two MRAC flies conspecific with D. varians is here designated as the lectotype of D. elegantula, while the second specimen (no head) is designated as paralectotype. The third MRAC fly, conspecific with D. aethiopica, also becomes a paralectotype. D. elegantula is now proposed as new junior synonym of D. varians.
Diopsis mayae Feijen & Feijen
Diopsis mayae Feijen & Feijen, 2017: 62 – holotype from Malawi, Kasungu National Park, Lifupa, 13°3’24”S 33°9’26”E in RMNH, large series of paratypes from Malawi, Mozambique and Tanzania in RMNH.
Anterior view of head or central head. – 5, Sphyracephala beccarii, female, Saudi-Arabia, Wadi-Maharish; 6, Diopsis mayae, female, Mozambique, Namaacha; 7, Diopsis mayae, male, South Africa, Pietermaritzburg; 8, Chaetodiopsis meigenii, female, Namibia, Katima; 9, Diasemopsis aethiopica, male, DR Congo, Mboma; 10, Diopsis arabica, female, Saudi-Arabia, Jebel Fifa. Scale bars = 0.5 mm, photographs Cobi Feijen.
Citation: Tijdschrift voor Entomologie 160, 2 (2017) ; 10.1163/22119434-00002065
Not Diopsis apicalis Dalman, 1817: 216 – holotype from Sierra Leone, in NHRS. Ref.: Feijen 1987.
Diopsis apicalis, Dawah & Abdullah 2008 (misidentification).
Diopsis apicalis, El-Hawagry et al. 2013 (misidentification).
Diopsis apicalis, El-Hawagry et al. 2016 (misidentification).
Distribution. Angola, Botswana, Central African Republic, DR Congo, Egypt, Ethiopia, Kenya, Malawi, Mozambique, Namibia, Saudi Arabia, Somalia, South Africa, South Sudan, Swaziland, Tanzania, Uganda, Yemen, Zambia, Zimbabwe.
Arabian records. Saudi Arabia, 1♀, 1♂, Wadi Minsah, 20°41’N 40°40’E, 550 m, 7–8.iv.1983, W. Büttiker (RMNH); 2♀, Asir, Jaheri, 16°33’N 43°3’E, 11.iii.1971, G. Popov (BMNH); 4♀, 1♂, Asir, Wadi Hali, 18°36’N 41°18’E, 420 m?, 9.i.2003, H.A. Dawah (Dawah & Abdullah 2008) (NMWC, NHMCSA); 1♀, 1♂, Asir, Maraba, 17°54’N 42°23’ E, 350 m? (Dawah & Abdullah 2008) (NMWC, NHMCSA); 5♀, 4♂, Albahha, De Al-Ain, 20°0’N 41°28’E, 3.iv.2003 (Dawah & Abdullah 2008) (NMWC, NHMCSA); Al-Mekhwa, 19°46’14”N 41°26’3”E, 350 m, xii–ii.2008–2012 (El-Hawagry et al., 2013) (KSMA); Dhee Ain, 19°33’16”N 41°15’46”E, 155 m, ii–v.2008–2012 (El-Hawagry et al., 2013) (KSMA); Jabal Shada al-A’la Nature Reserve, 19°50’35”N 41°18’42”E and 19°50’25”N 41°18’41”E, 5.v.2015 (El-Hawagry et al., 2016) (KSMA); Yemen, 5♀, 1♂, Mukeras, (Mukayris?), 13°56’N 45°40’E, 2159 m, i.1936, R.C.M. Darling (BMNH); 2♀, Wadi Lejij, Jebel Jihaf, 13°44’N 44°40’E, 7000 ft, 1.x.1937, H. Scott & E.B. Britton; 3♀, 2♂, Wadi Dareija, SW of Dhala, 13°40’45”N 44°42’7”E, 4500 ft, 6/9.ix.1937, H. Scott & E.B. Britton (BMNH); 9♀, 6♂, Usaifira, 1 mile N of Ta’izz, 13°38’N 44°1’E, 4500 ft, 21.xii.1937, H. Scott & E.B. Britton (BMNH); 8♀, 8♂, 1?, Wadi Jaira, tributary of Wadi Siham, 14°52’N 43°46’E, 3000 ft, 10.iii.1938, H. Scott & E.B. Britton (BMNH). Distribution records are mapped in Fig. 3.
Remarks. As indicated by Feijen (1987) and Feijen & Feijen (2017), many of the recordings for D. apicalis (or its junior synonym D. tenuipes Westwood) are misidentifications, involving one of the few other described Diopsis with an apical wing spot, or one of the more than 60 undescribed Diopsis with such a wing spot. Diopsis apicalis, as defined by Feijen 1987 and Feijen & Feijen (2017), has a West-African distribution from Mauritania to Chad and to Gabon. It is the dominant West-African species of the D. apicalis species group (Feijen & Feijen 2012). In eastern and southern Africa it is replaced by the also very abundant D. mayae, which even expands into Egypt and the Arabian Peninsula. Diopsis mayae is the sister species of D. apicalis.
Diopsis arabica Westwood
Diopsis arabica Westwood, 1837b: 544 – in Arabiâ desertâ. Type in ZMHB lost after 1941 (see Rohlfien & Ewald 1970). Ref.: Hennig 1941, Steyskal 1972, Cogan & Shillito 1980, Feijen 1989.
Teleopsis arabica, Rondani 1875: 443. Ref.: Brunetti 1928, Hennig 1941, Shillito 1971.
Diopsis collaris, Dawah & Abdullah 2008 (misidentification).
Diopsis collaris, El-Hawagry et al. 2015 (misidentification).
Distribution. Arabian Peninsula, but perhaps also Eritrea.
Arabian records. Saudi Arabia, 1♀, 1♂, Asir, Jaheri, 16°33’N 43°3’E, 11.iii.1971, G. Popov (BMNH); 1♀, Fifa, nr. Gizan, Jebel Fifa, 17°15’N 43°06’E, ~1240 m, 15.vii.1981, A.S. Talhouk (NHMB); 2♂, Asir, Wadi Hali,18°36’N 41°18’E, 420 m? 9.i.2003 (Dawah & Abdullah 2008) (NMWC, NHMCSA); 3♀, 2♂, Albahha, De Al-Ain, 20°0’N 41°28’E, 3.iv.2003 (Dawah & Abdullah 2008) (NMWC, NHMCSA); 13♀, 7♂, Maraba, Asir, 17°54’N 42°23’E, 15.viii.2004, 15.x.2004, 17.xi.2004, 15.xii.2004, 4.ii.2005, 17.iii.2005, 3.v.2005 (Dawah & Abdullah 2008), (NMWC & NHMCSA); Yemen, 6♀, 2?, Usaifira, 1 mile N of Ta’izz, 13°38’N 44°1’E, 4500 ft, 21.xii.1937, H. Scott & E.B. Britton (BMNH); 3♀, 1♂, Wadi Jaira, tributary of Wadi Sihan, 14°52’N 43°46’E, 3000 ft, 10.iii.1938, H. Scott & E.B. Britton (BMNH); 1♀, 1♂, 1?, Wadi Tiban, NW of Jebel Jihaf, 13°47’N 44°34’E, 3800 ft, 21.x.1937, H. Scott & E.B. Britton (BMNH). Distribution records are mapped in Fig. 4.
Remarks. In Africa the number of Diopsis species with a preapical wing spot is high. This group is referred to as the D. ichneumonea species group (Feijen & Feijen 2009) and counts 13 recognized African species and D. arabica. Most species in this group remain to be described. Four of the presently recognized species have a red collar: D. ichneumonea Linnaeus, D. pallida Westwood, D. collaris Westwood and D. arabica. Important external characters in this group are: shape of body (slender forest species or more broadly built species from open country), shape of preapical wing spot, pollinosity pattern of thorax, external structure of scutum (smooth or granular) and colour of collar. As far as we know there are no species in this group with a large distribution. West African species do not occur in East Africa and vice versa. Westwood (1837a) described D. collaris from Senegal while his D. arabica came from Arabia. The thorax of D. collaris he described as largely “niger, nitidus”, while the thorax of D. arabica was described as “sericeo-niger”, i.e. pollinose. Feijen (1989) indicated that the “D. ichneumonea” from Eritrea recorded by Frey (1921) could have been a D. arabica. The Arabian species identified by Dawah & Abdullah (2008) and El-Hawagry et al. (2015) as D. collaris should now be regarded as records for D. arabica.
Diopsis sp.
Diopsis sp. This species also belongs to the D. ichneumonea species group, but it could not be assigned to a described species and is most likely undescribed. However, describing and redescribing the many species (>50) in this probably not even monophyletic species group is a major job.
Distribution. Possibly Arabian Peninsula only.
Arabian records. Yemen, 1♀, 2♂, Usaifira, 1 mile N of Ta’izz, 13°38’N 44°1’E, 4500 ft, 21.xii.1937, H. Scott & E.B. Britton (BMNH); 3♀, 1♂, Jebel Jihaf, Wadi Leje, 13°27’N 44°26’E, 6800 ft, 13–15.x.1937, H. Scott & E.B. Britton (BMNH); 1♀, Wadi Jaira, tributary of Wadi Sihan, 14°52’N 43°46’E, 3000 ft, 10.iii.1938, H. Scott & E.B. Britton (BMNH). Distribution records are mapped in Fig. 4.
Remarks. This Diopsis from the ichneumonea species group can readily be distinguished from D. arabica by its black collar. In D. arabica the collar is reddish brown. Colour of the collar is a major character in this species group.
A key to the Diopsidae in Arabia
-
1.
Arista tripartite; eye stalk stout (~0.70× the widest sagittal eye diameter, Fig. 5), alula present (Fig. 11); vein CuA+CuP extending past cell cua; apical seta more than three times the scutellar spine length; syntergum only with terga 1+2 ...............
Sphyracephala beccarii
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–
Arista bipartite; eye stalk slender (<0.30× the eye diameter, Fig. 7), alula absent (Figs 12–15); vein CuA+CuP not extending past cell cua; apical seta usually shorter than scutellar spine or absent; syntergum including terga 1+2+3; DIOPSINAE ....................2
Figs 11–15. Dorsal view of wing. – 11, Sphyracephala beccarii, female, Saudi-Arabia, Wadi-Maharish; 12, Chaetodiopsis meigenii, male, DR Congo, Bomane; 13, Diasemopsis aethiopica, female, Togo, Amoutchou; 14, Diopsis mayae, male, Mozambique, Buzi; 15, Diopsis arabica, female, Saudi-Arabia, Jebel Fifa. Scale bars = 1 mm, photographs Cobi Feijen.
Citation: Tijdschrift voor Entomologie 160, 2 (2017) ; 10.1163/22119434-00002065
-
–
Arista bipartite; eye stalk slender (<0.30× the eye diameter, Fig. 7), alula absent (Figs 12–15); vein CuA+CuP not extending past cell cua; apical seta usually shorter than scutellar spine or absent; syntergum including terga 1+2+3; DIOPSINAE ....................2
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2.
Front femur with two rows of spinous setae around two rows of tubercles; apical seta present on scutellar spine; abdomen dark with pattern of silvery-grey pollinosity; two spermathecae; DIASEMOPSIS GENUS GROUP ........................3
- – Front femur only with two rows of tubercles; apical seta absent on scutellar spine; abdomen yellowish to reddish brown without pollinosity patterns; three spermathecae; DIOPSIS ...........................4
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3.
Central head almost rectangular in anterior view, face black and smooth, distinct facial teeth, frons with ribbed structure centrally (Fig. 8); wing with narrow central band (including two darker spots) and small apical spot (Fig. 12); abdomen distally broad and rounded; distinct suture between surstyli and epandrium ...............
Chaetodiopsis meigenii
- – Central head distinctly tapering ventrally (almost triangular in males with large stalks), frons and face brownish with paler brown spots, no facial teeth, frons smooth centrally (Fig. 9); wing with very vague central and apical infuscation (Fig. 13); abdomen slender, tapering apically; surstyli seamlessly fused with epandrium ......................... Diasemopsis aethiopica
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4.
Central head trapezoid (Fig. 6); wing with large rounded apical wing spot (Fig. 14); scutum largely glossy; surstyli fused to epandrium ........................
Diopsis mayae
- – Central head rounded (Fig. 10); wing with preapical wing spot (Fig. 15); scutum largely thinly pollinose; surstyli articulate .......................5
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5.
Collar reddish brown ................
Diopsis arabica
- – Collar black .................... Diopsis sp. (ichneumonea species group)
Biogeographical aspects of the Diopsidae in Arabia
Diopsidae chiefly occur in the Afrotropical and Oriental Regions. In the Nearctic Region two species of Sphyracephala occur (Feijen 1989). In the Australasian Region undescribed Sphyracephala species occur in the Solomon Islands and on New Guinea. On Taiwan, with both Palaearctic and Oriental aspects, two species occur: Megalabops bigotii (Hendel) and an undescribed Sphyracephala from the detrahens species group (see Feijen 1989). Likewise in the biogeographically hybrid Yaeyama Islands of Japan an undescribed Sphyracephala from the detrahens species group occurs (Ôhara 1993). In the undisputed Palaearctic Region three Sphyracephala species occur in, respectively, 1) Hungary and Serbia, 2) Azerbaijan and 3) Russia (Primorsky Krai) and Manchuria. A record of an unidentified Diopsis in Greece (Anagnou-Veroniki et al. 2008), probably represents an isolated case of introduction into the rice fields. From Europe, extinct Prosphyracephala are known from both amber and oil-shale sediments (see Kotrba 2009).
From the Afrotropical Region two intrusions of Diopsidae into Palaearctic North Africa are known. Sphyracephala beccarii was listed by Bezzi (1922) and Vaillant (1953) for El-Kantara in northern Algeria (not southern Algeria as mentioned by Vaillant). Ebrahim (2009) recorded for Egypt “D. apicalis”, a misidentification for D. mayae. The flies were collected in 1963 in Armant, near Luxor, not in the more northern Assiut as stated by Ebrahim.
A regularly returning discussion in papers on the Fauna of the Arabian Peninsula concerns the delimitation of the Afrotropical and Palaearctic Regions (e.g. Roselaar 2006, Kirk-Spriggs & McGregor 2009, El-Hawagry et al. 2013). Sclater (1858) and Wallace (1876) identified the Palaearctic and Ethiopian (later named Afrotropical) Regions. A transitional Eremic or Saharo-Sindian Region was later also proposed. Wallace defined as border between the Palaearctic and Ethiopian regions in the Arabian Peninsula the Tropic of Cancer (~23°26’N). Later authors varied this border between 21°N and 28°N (see Roselaar 2006). For practical reasons, Crosskey (1980) used for his catalogue of Afrotropical Diptera as border of the Afrotropical Region in the peninsula the northern boundaries of the modern state of Yemen. For birds, Martins & Hirschfeld (1994) included the entire peninsula in the Palaearctic Region, with the exception of the mountains of southwest Saudi Arabia, Yemen, and southern Oman. Roselaar (2006) proposed for the peninsula a revised southern boundary of the Palaearctic Region which included the entire peninsula except the Afrotropical Mountains of the south and southwest and the Oriental coastal plain of northern Oman. Based on studies of Diptera, Kirk-Spriggs & McGregor (2009) indicated that Wallace’s concept of the extent of the Afrotropical Arabian Peninsula is more accurate than Crosskey’s concept of Yemen alone. Based on various Diptera families they supported the view that northern Oman is the easternmost limit of the Afrotropical Region. El-Hawagry et al. (2013, 2015) studied a large set of insect orders in Al-Baha Province in Saudi Arabia and concluded that this province ought to be considered part of the Afrotropical Region rather than the Palaearctic Region.
The distribution of the six Diopsidae species in the Arabian Peninsula is presented in Figs 1–4. Four of these six species (S. beccarii, C. meigenii, D. aethiopica and D. mayae) belong to the small group of very common diopsids with an extensive distribution in Sub-Saharan Africa, while at least one more species (D. arabica) probably also occurs in Eritrea. S. beccarii is known from Algeria and D. mayae from Egypt, both Palaearctic countries. The distribution of the Diopsidae in the Arabian Peninsula concentrates on the mainly mountainous region from Al-Baha Province in Saudi Arabia to the southern tip of Yemen. In addition, C. meigenii (Fig. 2) also occurs in the south-western tip of Oman. Sphyracephala beccarii (Fig. 1) has the most widespread distribution of the diopsids in the peninsula, extending into what is here considered as the Palaearctic area of the United Arab Emirates. The rather limited viewpoint based on the distribution of Diopsidae tends to support the view that the Afrotropical Region in the Arabian Peninsula consists of the mountainous areas of southwest Saudi Arabia, Yemen, and southern Oman. The distribution of S. beccarii in the peninsula confirms its status as the most widespread of all Diopsidae, extending from Algeria to South Africa and from Madagascar to the United Arab Emirates. Hennig’s (1941) doubt concerning D. arabica “Es ist daher nicht sicher, ob er im paläarktischen oder äthiopischen Teil Arabiens gefangen wurde” can now be solved: this species only occurs in the Afrotropical part of the Arab Peninsula.
Description of a cluster of S. beccarii flies in Wadi Darbat, Oman
On 10.ix.2014, 11 am, while birding in Wadi Darbat (altitude 206 m) in the southern Sultanate of Oman, S. & M. Kühn, T. Wulf and R. Martin discovered a cluster of S. beccarii flies. The cluster was on the bark of live tree trunks next to the river and at a height of 0.5–3 m on the shaded side of the tree. The wadi itself is rocky with partly steep slopes and cliffs. The site (Fig. 16) is sheltered from the wind and thanks to the river more humid than the surrounding areas. The air temperature was around 35°C.
The fly cluster (Figs 17, 18, 20) consisted of one major and about ten smaller clusters. Additionally, many flies were well spread over the trunk. At the edge of the clusters few single S. beccarii could be found. An area of about 35 dm2 was occupied very densely with more than 15 flies per cm2. These densely covered areas counted several layers of flies (Fig. 20). In addition, an area of at least 1.4 m2 was covered with more than two flies per cm2. Based on these numbers there were at least 52,500 flies in the densely occupied areas and about 28,000 flies in the more sparsely covered areas. Altogether this leads to a total of at least 80,500 specimens of S. beccarii. No particular smell was noted around the cluster.
The flies were walking around in the clusters, therefore the clusters were changing shape and, likewise the numbers of flies in the various aggregations were changing during our observation. Few flies were seen flying around. When approached carefully, the flies didn’t react. However, when we made quick movements, they flew up. Neither in the field nor on the photos, was any sign of intraspecific aggression noted. The cluster consisted of males and females, but no mating behaviour was observed. Close to the cluster a solitary C. meigenii was observed (Figs 18, 19).
Wadi Darbat, Sultanate of Oman, 10.xi.2014. – 16, habitat of the Wadi; 17, overview of clusters of Sphyracephala beccarii on tree trunk, dark sections are clusters, specks on pale sections are individual flies; 18, detail of cluster of Sphyracephala beccarii, single Chaetodiopsis meigenii in lower left corner; 19, Chaetodiopsis meigenii near cluster. Photographs 16, 17 Martin Kühn; photographs 18, 19 Ralph Martin.
Citation: Tijdschrift voor Entomologie 160, 2 (2017) ; 10.1163/22119434-00002065
A review of clustering in Diopsidae
Large to huge aggregations of Diopsidae are very common in the Afrotropical Region, especially in the dry season. They can be found along rivers or lakes and in swampy areas or rain forests. These aggregations can count thousands of specimens and can include 10–20 species (Feijen, 1989 and later personal observations). In the Oriental Region large aggregations appear to be much less common, although they have sometimes been reported (Westwood 1837a, Koningsberger 1915).
A different issue in Diopsidae is the formation of clusters. The differences between clusters and aggregations can be pointed out to be that clusters are much denser and can count tens of thousands of normally conspecific flies. Occasionally a few specimens of another species can occur in a cluster, while only a few cases of really mixed clusters are known (see below). As the defining character of clusters the formation of real layers of flies should be indicated (Figs 20, 21). Flies then sit in a haphazard, random way on top of each other.
Clusters in Diopsidae. – 20, Wadi Darbat, Sultanate of Oman, 10.xi.2014, detail of cluster of Sphyracephala beccarii showing layered structure (photograph Ralph Martin); 21, Matema, Tanzania, 6.vi.2014, cluster of Diasemopsis varians with some Sphyracephala munroi in between, note densely layered structure on lower leaf just left of centre (photograph Martin Grimm).
Citation: Tijdschrift voor Entomologie 160, 2 (2017) ; 10.1163/22119434-00002065
Kavanaugh (1977), working on carabid beetles, later supported by Arnaud (1983), describing the phenomenon in a kelp fly, listed as possible mechanisms for the formation of aggregations:
- 1. “Independent, individual response to an environmental gradient (or gradients) leading to aggregation in an environmentally (abiotically) optimum location.”
- 2. “Individual response to some stimulus (or stimuli) provided by other individuals, leading to aggregation at a common location.”
- 3. “A combination of the first two.”
The first mechanism could also be described as a more passive system, leading to “non-intended” aggregations, while in the second one an active system leads to aggregations. In Diopsidae the first mechanism could account for aggregations as found in the dry season in Africa, while the second mechanism appears more likely in the formation of clusters.
Reports on clusters in the Diopsidae all refer to species of Sphyracephala. Brunetti (1907, 1919) was the first one to mention “vast numbers” for Sphyracephala hearseiana (Westwood). He recorded these Indian flies “in profusion under a low arch over a roadside ditch in Cawnpore” on or around 30.xi.1904. Furthermore, he mentioned these flies were “clustered very thickly together on the inside walls of the ground floor of that deserted building” of the old Residency at Lucknow on 4.xii.1904. Sen (1922) described a number of additional clusters for S. hearseiana and also provided the first photograph of a cluster. All observations were in wintertime and at altitudes of 100–300 metres. One exception was formed by a cluster in early June but that was at around 1500 m and under very dry conditions. All cases concerned secluded positions: ceiling of culverts, among roots overhanging drains, bushes overhanging a small stream and the shady face of a rock overhanging a pool. Sen observed: “On passing a net over them they rose with a roar like a swarm of bees and a solid mass of several handsful (sic!) of flies was got in the net. Apparently the flies were originally congregated in a mass several individuals (? several inches) deep. The mass consisted of flies of both sexes, in approximately equal numbers.” Mathur (1957) found “large congregations” of S. hearseiana in wintertime (November–February). Mathur remarked “Each cluster appears as a large compact black mass of spot on the wall” and “They are readily disturbed with one’s breath, and quickly fly about and settle on anything near-about”. The clusters were calculated (“estimated”) to be composed of between 4,762 and 50,952 specimens.
In the Nearctic Region, Flint (1956), Lavigne (1962) and Hochberg Stasny (1985) reported on clusters of S. brevicornis (Say) at their overwintering site. These authors did not distinguish between S. brevicornis and S. subbifasciata Fitch, so the latter species might also have been involved. Flint found clusters in a “small crack between two large blocks” and remarked “Undoubtedly there were thousands present” and “over 150 were taken with a small killing vial before they all flew away”. Lavigne stated that “Mating occurs almost immediately after the adults come out of hibernation, while they are still clustered at the overwintering site”.
In Algeria, in July 1949 Vaillant (1953) found among rocks in an oasis “de véritables essaims de Sphyracephala Beccarii”. Feijen (1984) found in the dry season (22.viii.1974, Diampwe River, 1152 m) in Malawi among rocks in a river bedding a dense mass of S. beccarii. After being disturbed they flew up in a dense cloud. A single sweep of the net yielded more than 6,000 specimens, the size of the whole mass estimated to be in the order of 100,000 specimens. The percentage ♀♀ came to 47%.
Reports on cluster formation in other Diopsidae genera are rare. Marion Kotrba (pers. comm.) observed cluster formation in Howick (South Africa) in early May 1992. This involved Diopsis mayae and a species of the Diopsis atricapilla species group. These flies already formed dense aggregations during the day. At late dusk, they flew away under a bush. There, Kotrba found them in the early morning gathered on a single, kinked stem of grass, on the part that was hanging down. The cluster was really dense and several flies deep, like a bee swarm. When she tried to collect them, she touched the grass and all flies were up and flying within an instant. Martin Grimm (pers. comm.) observed and photographed clusters in Matema, Tanzania, on 6.vi.2014 at around 11 o’clock a.m. The clusters (Fig. 21) mainly consisted of Dia. varians, but in between were also S. munroi Curran and a few S. beccarii. The clusters were on leaves around 1.5 m above a small montane river in the forest. The place was somewhat cooler than the further ambient temperature of 28–30°. In Maputo, Mozambique, the first and third author several times found clusters of C. meigenii on lower leaves of garden shrubs. This was in the cold season (June–July) and involved several thousands of flies. A curious ad hoc cluster was once observed in Malawi by the first and third author. Very early in the morning, on an unusually cold day, they visited a rice scheme to collect samples of rice hills. While changing into rubber boots, they left their shoes on a paddy bund. Returning some 30 minutes later, they noted that their shoes were covered by layers of Diopsis longicornis Macquart, the well-known rice stem-borer. The only explanation could be that the flies were attracted to the warm temperature of the shoes. This phenomenon was never observed again during many years of study of D. longicornis. The only other occasion involving this species was on 26.vi.1974 at the Khanda River (Chilwa Plain, Malawi, 675 m) when the same observers noted a dense cluster of thousands of D. longicornis and D. mayae in a clump of reeds. At the same location, aggregations were regularly observed, but only this once a real cluster was involved.
It appears certain that real clusters of diopsids, involving massive numbers of up to 100,000 specimens, can only be the result of the second mechanism stated by Kavanaugh (1977): individual response to some stimulus (or stimuli) provided by other individuals. Initial aggregation in an environmentally optimum location can play a part just as well. The phenomenon of cluster formation, especially in Sphyracephala, appears clearly linked to the process of hibernation or estivation. In clusters, mating behaviour has never been observed. Lavigne (1962) observed that mating occurs almost immediately after the hibernation period. It appears to be a common character for Diopsidae clusters that, when even superficially disturbed, the flies can immediately fly up en masse. This is the more striking as it happens also during the estivation or hibernation period with assumed lower rates of metabolism. It seems likely that the explanation for the occurrence of multi-layer clusters in Diopsidae must be sought in the direction of maintenance of an optimal micro-habitat. The maintenance of a certain level of temperature and perhaps also humidity, would then enable the flies to react very fast to disturbance. The importance of temperature is clearly shown by the behaviour of D. longicornis on the bund in Malawi.
In the Oriental Region a common, but not related, aggregation phenomenon occurs in the diopsid genera Teleopsis Rondani and Cyrtodiopsis Frey. These aggregations have been referred to as sleeping communities or societies, nocturnal clusters, nocturnal lekking aggregations, harems and aggregations on nocturnal roosting sites (de la Motte & Burkhardt1983, Wilkinson & Dodson 1997, Cotton et al. 2015). Typically, flies gather at dusk in relatively small conspecific aggregations on thread-like hanging vegetation. Males engage in ritualized fights to win a harem (de la Motte & Burkhardt 1983), while “The vast majority of matings occur in these aggregations during the dawn and dusk period, when males attempt to mate with females in their harem” (Cotton et al. 2015).
Martin & Susanne Kühn made two of the Oman photographs available, while Martin Grimm supplied the photograph of a Diasemopsis cluster in Tanzania. We are grateful to Martin Hauser, Martin Grimm and Marion Kotrba for discussions about cluster formation. Daniel Whitmore (BMNH) and Eliane De Coninck (MRAC) provided access to the Diopsidae collection of their museums. The original idea for a paper on Arabian Diopsidae came from Prof. Dr William Büttiker-Otto (1921–2009), who proposed it to the first author in 1989. The comments by anonymous referees are greatly appreciated.
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