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

Published as part of 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, pp. 563-570 in Zootaxa 4990 (3) on pages 565-566, DOI: 10.11646/zootaxa.4990.3.7, http://zenodo.org/record/5027283