Dasyrhicnoessa insularis ( Aldrich, 1931 )

Munari, Lorenzo, Kirk-Spriggs, Ashley H. & Mcgregor, Gillian K., 2020, The beach flies of the Mascarene Islands (Diptera: Canacidae: Tethininae), Zootaxa 4853 (2), pp. 183-198 : 192-193

Dasyrhicnoessa insularis ( Aldrich, 1931)

Figs 10 , 16 , 24 , 27 , 32 .

Distribution. Afrotropical: Cameroon, Madagascar, Mascarenes ( La Réunion *, Mauritius *, Rodrigues *), Nigeria, Seychelles ( Mahé), Sierra Leone. Australasian/Oceanian: American Samoa (Tutuila), Australia (Queensland), Austral Islands, Bismarck Islands (Dyaul), Canton Island, Caroline Islands (Ponhpei, Chuuk, Yap, Palau), Fiji Islands (Ovalau, Suva, Vanua Balavu, Viti Levu),? French Polynesia (Society Islands: Moorea), Hawaii (French Frigate Shoals, Hawaii, Hilo, Kahoolawe, Kauai, Lisiansky, Maui, Midway Atoll, Molokai, Oahu, Pearl and Hermes Reef), Kiribati (Butaritari, Makin, Eita, Tarawa, Abemama), Line Islands (Christmas), Mariana Islands (Saipan, Tinian), Marquesas (Hivaoa, Nuku Hiva), Marshall Islands (Majuro, Japtan, Parry, Lib, Jibu, Jaluit, Namorik), Palmyra Island, Pitcairn Island, Rapa Island, Society Islands (Bora Bora, Raiatea, Tahiti), Vanuatu (Erromanga, Aneityum), Wake Island. Nearctic: Bermuda, United States (Florida). Neotropical: Bahamas (South Bimini), Belize, Brazil (Ceará, Paraná, São Paulo), Mexico (Tabasco), West Indies ( Cuba, Dominica, St. Kitts, St. Lucia, St. Vincent). Oriental: Chagos, Indonesia (Sulawesi, Ternate).

Material examined (all “A.H. Kirk-Spriggs & B.S. Muller, sweeping intertidal zone and coastal vegetation”, unless otherwise stated). La Réunion: 1♀, Grande Anse , 21°22′17″S, 55°33′00″E, 26.x.2015 , 0–12 m, M.J. Ebejer, general sweeping; secondary forest, intertidal rocks & coral beach (deposited MJEC) ; 1♂, St.-Louis, Rivière St.-Étienne , 21°17′54″S, 55°24′07″E, 0–9 m, 18.x.2015 , M.J. Ebejer, general sweeping; intertidal rocks & vegetated gravel plain (deposited MJEC); 1♀, St.-Pierre, Pointe de Pont , 21°20′51″S, 55°28′52″E, 0–6 m, sweeping intertidal rocks and coral beach, 13.xi.2015 , A.H. Kirk Spriggs. Mauritius: 14♂, 11♀, Black River, Le Morne Brabant , 20°27′32″S, 57°19′42″E, 1–3 m, 28.i.2018 (1♀ deposited LMC) ; 63♂, 35♀, Black River, Petite Case Noyale , 20°24′23″S, 57°22′10″E, 1–3 m, 28.i.2018 (2♂ deposited LMC) ; 3♂, 4♀, Black River, Tamarin , 20°19′41″S, 57°22′33″E, 1–3 m, 28.i.2018 ; 23♂, 86♀, Grand Port, Grand Sable , 20°19′12″S, 57°46′12″E, 1–3 m, 27.i.2018 (2♂, 1♀ deposited LMC) ; 8♂, 8♀, Grand Port, Pointe d’Esny , 20°25′28″S, 57°43′22″E, 1–3 m, 27.i.2018 (1♀ deposited LMC) ; 4♂, 4♀, Grand Port, Vieux Grand Port, 20°22′23″S, 57°42′48″E, 1–3 m, 27.i.2018 (1♂ deposited LMC) ; 4♂, 1♀, Pamplemousses, Le Goulet , 20°06′14″S, 57°31′02″E, 1–3 m, 30.i.2018 ; 9♂, 12♀, Pamplemousses, Tombeau Bay , 20°08′00″S, 57°29′54″E, 1–3 m, 30.i.2018 (1♀ deposited LMC) ; 2♀, Pamplemousses, Trou aux Biches, 20°02′36″S, 57°32′14″E, 1–3 m, 29–30.i.2018 ; 2♂, 6♀, Rivière du Rempart, Pointe des Lascars , 20°05′14″S, 57°42′26″E, 1–3 m, 31.i.2018 ; 5♂, 3♀, Savanne, Bel Ombre , 20°30′00″S, 57°23′34″E, 1 m, sweeping coastal rocks and sandy beach, 11.xii.2016 (1♂ deposited LMC) ; 3♂, 2♀, Savanne, Bel Ombre , 20°29′32″S, 57°22′42″E, 1–3 m, 26.i.2018 ; 2♀, Savanne, Riambel , 20°31′09″S, 57°30′25″E, 1–3 m, 26.i.2018 . Rodrigues: 2♂, 2♀, Anse aux Anglais , 19°40′15″S, 63°26′19″E, 1–3 m, 10.ii.2018 (1♂, 1♀ deposited LMC) ; 2♀, Anse Mourouk , 19°44′23″S, 63°27′53″E, 1–3 m, 10.ii.2018 ; 15♂, 11♀, Baie du Nord , 19°42′33″S, 63°22′20″E, 1–3 m, 9.ii.2018 (1♀ deposited LMC) ; 1♀, Île Michel , 19°44′43″S, 63°24′13″E, 1–3 m, 10.ii.2018 ; 2♀, Plaine Corail , 19°46′05″S, 63°22′36″E, 1–3 m, 9.ii.2018 (all deposited BMSA, unless otherwise stated).

Comments: A common pantropical beach fly. In this species the colour of the thorax often exhibits strong variation. The following range of variation has been observed in specimens from different world sites: mesonotum entirely yellow to blackish, sometimes scutum dark brown and scutellum yellow only at margin; in a few cases, scutum dark brown and scutellum predominantly yellow. Though rather infrequent, some transitional forms occur in formerly studied specimens ( Munari 2002). The above is not corroborated by the material from the Mascarenes, which does not exhibit significant variation in mesonotal colour, the yellow or sometimes yellowish fulvous colours being invariably present, to a greater or lesser extent on the scutum. Similar to other Indo-Pacific congeners, the posteroventral armature of the male mid femur is formed of a long row of regular, spine-like setae, gently decreasing in size towards the apex of the femur.

Figures

FIGURES 10–12. Mid femora and tibiae of male beach flies (posterior views). 10. Dasyrhicnoessa insularis (Aldrich). 11. D. ferruginea (Lamb). 12. D. vockerothi Hardy & Delfinado. Scale bar = 0.3 mm.

FIGURES 13–18. Male terminalia of beach flies. 13. Afrotethina aurisetulosa (Lamb), right surstyli in posteromesial view (after Munari 1988). 14. Pseudorhicnoessa rattii Munari, left lateral view (after Munari 1981). 15. Same, P. spinipes Malloch (after Sasakawa 1974). 16. Same, Dasyrhicnoessa insularis (Aldrich) (after Foster & Mathis 1998). 17. Same, D. vockerothi Hardy & Delfinado (after Sasakawa 1995). 18. Same, D. ferruginea (Lamb). Scale bars: 13 = 0.05 mm; 14–15 = 0.3 mm; 16–18 = 0.1 mm. Abbreviations: a sur—anterior surstylus; p sur—posterior surstylus.

FIGURES 22–24. Distribution maps of beach flies on La Réunion sampled in 2015. 22. Afrotethina aurisetulosa (Lamb). 23. Dasyrhicnoessa ferruginea (Lamb). 24. D. insularis (Aldrich).

FIGURES 25–29. Distribution maps of beach flies on Mauritius sampled in 2018. 25. Afrotethina aurisetulosa (Lamb). 26. Dasyrhicnoessa ferruginea (Lamb). 27. D. insularis (Aldrich). 28. D. vockerothi Hardy & Delfinado. 29. Pseudorhicnoessa rattii Munari.

FIGURES 30–34. Distribution maps of beach flies on Rodrigues sampled in 2018. 30. Afrotethina aurisetulosa (Lamb). 31. Dasyrhicnoessa ferruginea (Lamb). 32. D. insularis (Aldrich). 33. D. vockerothi Hardy & Delfinado. 34. Pseudorhicnoessa rattii Munari.