Isocanace Mathis, 1982

Munari, Lorenzo, Kirk-Spriggs, Ashley H. & Mcgregor, Gillian K., 2021, The surf flies of the Mascarene Islands (Diptera: Canacidae: Canacinae), with the description of a new species, Zootaxa 4990 (3), pp. 563-570 : 565-566

Key to Afrotropical Isocanace Mathis

1. Antennal arista with branches long ( Fig. 2 ), some almost double or more than aristal width at base; anepisternal and usually katepisternal setae pale, mostly yellow; male terminalia with posterior part of surstylus (in lateral view) with more or less prominent heel-shaped swelling ( Figs 4, 5 ) (Aldabra Is. & Madagascar).............................. I. briani Mathis

- Antennal arista with branches distinctly shorter ( Fig. 3 ), as long as, or marginally longer than, aristal width at base; anepisternal and katepisternal setae black; male terminalia (in lateral view) with posterior part of surstylus without heel-shaped swelling (e. g., Fig. 6 )......................................................................................... 2

2. Thorax with anterior notopleural seta present, although weaker and shorter than posterior seta; male terminalia (in lateral view) with surstylus lacking a protruding swelling on anteromedial part, but if swelling present, then this reduced in distal 2 / 3 of lateromedian side, bearing cluster of long setulae; surstylus (in lateral view) with gently curved, posteromedial margin, or otherwise, with apical 1 / 3 narrow and curved posteriorly ( Mathis 1999, fig. 14)............................................. 3

- Thorax with anterior notopleural seta absent or very weak and pale; male terminalia (in lateral view) with surstylus bearing strongly protruding swelling on anteromedial part; surstylus (in lateral view) with broadly curved posteromedial margin... 4

3. Male terminalia (in lateral view) not as described below, with surstylus very long and narrow, with subapical posterolateral swelling bearing cluster of pale setulae, apical 1 / 3 curved posteriorly ( Mathis 1999, fig. 14) ( Kenya & South Africa)............................................................................................. I. australis Mathis

- Male terminalia in lateral view with foot-like surstylus ( Fig. 6 ) (broadly resembling that of I. briani ( Figs 4, 5 ), but without posterior heel-shaped swelling), with proximal stem long and slender, neck-shaped, mid part moderately swollen, ending distally with anteriorly oriented, sickle-shaped, apical tip ( Mauritius)............................ I. mauritiana Munari sp. nov.

4. Head with 4 lateroclinate fronto-orbital setae; male terminalia with surstylus (in lateral view) narrow, sharply hooked apically, with narrow hook-like tip oriented anteriorly ( Mathis 1999, fig. 29) ( Democratic Republic of Congo)............................................................................................ I. flava (Canzoneri & Meneghini)

- Head with 3 lateroclinate fronto-orbital setae; male terminalia with surstylus (in lateral view) strongly broadened medially, tapered apically, with large triangular tip oriented anteriorly ( Mathis 1999, fig. 30) ( Kenya)............ I. freidbergi Mathis

Figures

FIGURES 2‒6. Antennae and male terminalia of surf flies. 2. Left antenna of Isocanace briani Mathis, lateral view (after Mathis 1982a, from a stereoscan micrograph). 3. Same, I. mauritiana sp. nov. (pubescence of postpedicel omitted); 4. Male left surstylus of I. briani, lateral view, exhibiting characteristic posterior “heel” (from type locality: Madagascar, Sambirano Lokobe Nossi-Be) (after Mathis 1982a). 5. Same, from Aldabra Is. (after Mathis 1982a). 6. Same, I. mauritiana sp. nov. Scale bars: 2‒3 = 0.2 mm; 4‒6 = 0.1 mm.