Pseudorhicnoessa rattii Munari, 1981

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 : 195-196

Pseudorhicnoessa rattii Munari, 1981

Figs 14 , 29 , 34 .

Distribution. Afrotropical: Mascarenes ( Mauritius, Rodrigues *), Seychelles (Cousine, Mahé). Oriental: India (Goa), Maldives, Sri Lanka.

Material examined (all “A.H. Kirk-Spriggs & B.S. Muller, sweeping intertidal zone and coastal vegetation”, unless otherwise stated). Mauritius: 1♀, Black River, Albion , 20°12′35″S, 57°24′13″E, 1–3 m, 28.i.2018 ; 1♀, Black River, Petite Case Noyale , 20°24′23″S, 57°22′10″E, 1–3 m, 28.i.2018 ; 45♂, 38♀, Black River, Tamarin , 20°19′41″S, 57°22′33″E, 1–3 m, 28.i.2018 (1♂, 3♀ deposited LMC) ; 4♂, 1♀, Flacq, Poste Lafayette , 20°07′02″S, 57°45′05″E, 1–3 m, 30.i.2018 (1♂ deposited LMC) ; 3♂, 6♀, Flacq, Trou d’Eau Douce , 20°14′20″S, 57°47′34″E, 1–3 m, 27.i.2018 ; 53♂, 111♀, Pamplemousses, Le Goulet , 20°06′14″S, 57°31′02″E, 1–3 m, 30.i.2018 (1♂ deposited LMC) ; 16♂, 22♀, Pamplemousses, Tombeau Bay , 20°08′00″S, 57°29′54″E, 1–3 m, 30.i.2018 (1♂ deposited LMC) ; 5♂, 4♀, Pamplemousses, Trou aux Biches , 20°02′36″S, 57°32′14″E, 1–3 m, 29–30.i.2018 ; 28♂, 23♀, Rivière du Rempart, Bain Boeuf , 19°59′13″S, 57°36′12″E, 1–3 m, 30.i.2018 (1♀ deposited LMC) ; 1♂, Rivière du Rempart, Grand Gaube , 20°01′00″S, 57°40′55″E, 1–3 m, 29–30.i.2018 ; 4♂, 1♀, Rivière du Rempart, Pointe des Lascars , 20°05′14″S, 57°42′26″E, 1–3 m, 31.i.2018 ; 1♀, Savanne, Bel Ombre , 20°30′00″S, 57°23′34″E, 1 m, 11.xii.2016 , sweeping coastal rocks and sandy beach; 5♂, 6♀, Savanne, Bel Ombre , 20°29′32″S, 57°22′42″E, 1–3 m, 26.i.2018 ; 33♂, 19♀, Savanne, Rivière des Galets , 20°30′04″S, 57°26′52″E, 1–3 m, 26.i.2018 (1♀ deposited LMC) . Rodrigues: 9♂, 1♀, Anse aux Anglais , 19°40′15″S, 63°26′19″E, 1–3 m, 10.ii.2018 ; 1♂, 2♀, Anse Mourouk , 19°44′23″S, 63°27′53″E, 1–3 m, 10.ii.2018 ; 5♂, 7♀, Petite Gravier , 19°43′40″S, 63°29′03″E, 1–3 m, 10.ii.2018 (1♂ deposited LMC) ; 1♂, Plaine Corail , 19°46′05″S, 63°22′36″E, 1–3 m, 9.ii.2018 ; 4♂, 2♀, Rivière Banane , 19°40′37″S, 63°28′30″E, 1–3 m, 10.ii.2018 (all deposited BMSA, unless otherwise stated).

Comments: The small genus Pseudorhicnoessa Malloch, 1914 , includes three described species, namely: P. rattii , exclusively inhabiting the seashores of the Indian Ocean, and the two very closely related P. longicerca Munari, 2014 and P. spinipes Malloch, 1914 , which are distributed in the western Pacific Ocean. Pseudorhicnoessa spinipes is widespread throughout the entire region, whereas P. longicerca is only known from Papua New Guinea. These two western Pacific species can only be differentiated morphologically based on differences in the male terminalia, while P. rattii exhibits a strikingly different shape of both the anterior and posterior surstyli ( Figs 14, 15 ). Aside from these obvious terminalia differences, P. rattii and the other two western Pacific species do not differ significantly in either their external characters or their general habitus; the habitus being extraordinarily similar in all three species. The slight male terminalia divergence in both P. longicerca and P. spinipes indicates a very recent process of sympatric speciation, while the vicariant P. rattii from the Indian Ocean (west of the Sunda Islands) probably diversified in relatively more ancient times. Pseudorhicnoessa rattii was previously recorded from Mauritius by Munari (1990) and is reported here for the first time from Rodrigues.

Figures

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 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.