Key to males of Myoplatypus . Total body lengths used in the key are taken from Table 1. Specimens should also be carefully compared with the photographs, bearing in mind body size.

1. Spines on ventrite 3 short (can be absent), as wide as tall; southeastern or southern USA (1 temperate species).... flavicornis

- Spines on ventrite 3 longer; collected from American tropics (9 tropical species)................................... 2

2. In addition to spines on ventrite 3, spines present on ventrite 4 (can be quite low or occasionally absent in brevicornis); mid- or upper-elevation species................................................................................. 3

- No paired spines on ventrite 4........................................................................... 4

3. Smaller, <4 mm long; interstriae 3 not ending in a prominent tooth..................................... quadricornis

- Larger,> 4.5 mm long; interstriae 3 ending in a prominent tooth........................................ brevicornis

4. Length about 2 mm; lowland species................................................................. sicarius

- Length about 3 mm or more (lowland or upland species)...................................................... 5

5. Simple declivity, partly covered in short dense setae; lowland species........................................ petrovi

- Declivity with strongly developed posterolateral angles (one sp. with only short, acute projections), never smooth with dense short setae; mid- to upper elevation species................................................................. 6

6. Declivity fairly simple, posterolateral angles forming an equilateral triangle; interstriae 1–4 carinate for at least final 1/3 of their length.................................................................................... nicaraguensis

- Declivity with posterolateral angles weakly to strongly produced horizontally; interstriae 1–4 carinate for final ¼ or less of their length.............................................................................................. 7

7. Interstriae 1 ending in a long, thick spine as long as posterolateral angle projection................................. 8

- Interstriae 1 not ending in a long thick spine................................................................ 9

8. Shorter, ca 4.0 mm.............................................................................. connexus

- Larger, ca 4.7 mm ................................................................................ senexus

9. Posterolateral angle produced into a horizontal long, blunt spine.......................................... biprorus

- Posterolateral angle produced downwards at an angle................................................... prenexus