Key to the adult Dixidae of southern Brazil

1. Wings with distinct spots in all cells......................................................... Dixella trinitensis

- Wings without spots or with only a faint spot at crossvein r-m.................................................. 2

2. Thorax (lateral view) with black stripe on dorsal portion and yellow on basal portion....................... Dixella limai

- Thorax (lateral view) brown (Fig. 2A; 7C), or yellow with pale brown spot on katepisternum (Fig. 5D)................. 3

3. Katepisternum yellow with distinct pale brown spot in middle-anterior portion (Fig. 5D)................... Dixella jailtoi

- Katepisternum uniformly brown (Fig. 2A; 7C).............................................................. 4

4. Male............................................................................................... 5

- Female............................................................................................. 6

5. Gonostylus triangular (lateral view) with stout setae (Fig. 8A)...................................... Dixella spinosa

- Gonostylus cylindrical without stout setae (Fig. 3A–E).......................................... Dixella moultoni

6. Sternite IX with robust wide lateral portion, without projection (Fig. 9B)............................. Dixella spinosa

- Sternite IX with slender lateral portion and small projection (Fig. 4B)............................... Dixella moultoni