Psacotes caudata, Jean- Paul Haenni & Dalton de Souza Amorim, 2016

Jean- Paul Haenni & Dalton de Souza Amorim, 2016, Two new Afrotropical genera of Scatopsidae (Diptera), Mitteilungen Der Schweizerischen Entomologischen Gesellschaft 89, pp. 127-142 : 138-140

Psacotes caudata sp. nov.

( Figs 24–26 )

Type locality. Botswana, Serowe.

Material. Holotype: male, labelled: « BOTSWANA: Serowe / Farmer’s Brigade / Aug 1991, SE2226BD / Per Forchhammer / Malaise Trap ». Holotype in poor condition (right wing lacking, apex of left wing damaged), [formerly dry-preserved, glued on card,] dissected and slide-mounted, CMNHP.

Diagnosis.Male aedeagal plate with an elongate, tail-like conical process ( Fig. 26 ).

Description.Male. Body length, 1.5 mm. Brown in general colour (but probably not fully coloured specimen), except palpus and labella, yellowish-brown, a median pale ring on posterior tibia, all tarsi contrastingly yellow; halter brown; dull, except for thoracic pleura, shining. Labella elongate, pointed; antenna as long as head height, widening towards apex, with a8-segmented flagellum, last segment rounded, somewhat longer than combined length of two preceding ones; each flagellomere bearing asingle row of setae; palpus very large, nearly as long as eye height, rounded at apex and base, sausage-shaped.

Thorax. Notum clearly longer than wide; awell marked row of 15 long supralars; 10 strong marginal scutellars; spiracular sclerite triangular, elongate, nearly twice as long as high; about 16 anepisternals and arow of about 10 upper anepisternals.

Abbreviations: ae – aedeagus; ae pl – aedeagal plate; ep – epandrium; pa – paramere.

Wing. 1.6 mm; membrane light whitish, anterior veins light brownish, posterior veins translucent; wing venation similar to that of P. gigantipalpus ;halter with 3setae on stem.

Abdomen. Sternites 1–2 unsclerotized, sternites 3–7 sclerotized, 3narrow, 4– 6wider, 7of normal size; pregenital segment 7with acomplete anterior ring of sclerotization, which is also present on pleural membranes, sternite and tergite very close together anteriorly, nearly fused, spiracles present basally on pleural membrane, close to tergite; both sternite and tergite 7( Figs 24–25 ) with acomplex posterior median emargination, aseparate, small inner sclerite at the posterior margin of tergite 7( Fig. 25 ).

Genital capsule ( Fig. 26 ) as high as long, with elongate, conical, tail-shaped prominent aedeagal plate, with arounded hole at base through which protrudes the short aedeagus; epandrium truncate apically, convex, somewhat roof-shaped, parameres widened, beak-like, directed dorsally, apically acute, setose.

Female. Unknown.

Distribution.Only known from the type-locality in Botswana.

Etymology.The specific epithet of the species name is afeminine adjective derived from the Latin word «cauda», meaning «tail», in reference to the striking tail-like projection of the male genital plate capsule.

Psacotes gen. nov. clearly belongs to the Scatopsinae , as can be inferred by considering the sperm pump lying free in the abdomen and other synapomorphies of the subfamily. Its tribal placement, however, is less evident. The Rhegmoclematini can be discarded, as there are setae on the stem on the halter and there are no macrosetae on the wing membrane or on posterior veins. The relatively short R4+5,the vestiture of microtrichia on most of the body, and the relatively simplified structure of the male terminalia would not allow its inclusion in the Scatopsini . At afirst look the male genital capsule is similar to that of the Colobostematini genus Colobostema Enderlein, 1926 , but this resemblance is superficial. In fact, the genus presents several synapomorphies of the Swammerdamellini or of some of its subclades ( Amorim 1982): antepronotum partly divided by aventral cleft, R 4+5 reaching C shortly beyond the middle of wing, and the presence of awell-developed aedeagal plate in the male terminalia. The type-species of the genus proposed here was originally described by Cook (1962) as belonging to the catch-all genus Rhexoza Enderlein. As amatter of fact, Rhexoza was originally understood by Cook (1956) in avery broad sense, grouping all Swammerdamellini species except for those placed in the genera Swammerdamella Enderlein and Coboldia Melander, 1916 (e.g., Cook 1965b). More recently, arguing that Rhexoza was polyphyletic, Cook (1975, 1978) erected new genera for different groups of species formerly included in the genus. Freeman (1990) and Amorim (2007) continued to dismantle Rhexoza describing several additional genera for species that belonged to Rhexoza s.l.

The sclerotized sternites 3–7 in the Afrotropical species gathered in this new genus suggest arather basal position within the tribe. This condition is seen in all genera of Swammerdamellini except Pararhexosa , Swammerdamella ,and Coboldia ,other genera of the tribe having gradually lost the sclerotization of sternites 3– 7. Very typical of Psacotes are its strongly developed maxillary palpi, to some extent similar to what is seen in the genus Pararhexosa .This new genus, however, strongly differs from the latter by the shape of the head, higher than long (longer than high in Pararhexosa ), the shape of the elongate spiracular sclerite (short, triangular in Pararhexosa ), and the well-developed aedeagal plate in the male terminalia (not present in Pararhexosa ). As seen above, Pararhexosa has some similarities with Aztecatopse and Octaseps . Psacotes in fact shares some apomorphic features with the terminal taxa of the Swammerdamellini: the antepronotum deeply incised ventrally (a division more advanced than in Abrhexosa Freeman, 1990 or Cooka Amorim, 2007 , but less complete than in Brahemyia Amorim, 2007 ), considerably short aedeagus, protruding through arounded hole in the basal part of the strongly developed aedeagal plate (as in Brahemyia ). The sclerotized abdominal sternite 4 (unsclerotized in Abrhexosa , Quateiella , Cooka and Brahemyia )in Psacotes ,however, is aplesiomorphic condition that does not allow it to fit close to these three genera. Aformal phylogenetic analysis of the Swammerdamellini is still necessary to properly establish the relationships between the genera of the tribe.

Figures

Figs 24 – 26. Psacotes caudata sp. nov. ♂: — 24. Tergite 7; — 25. Sternite 7; — 26. Genital capsule, lateral view.