Key to the Costa Rican species of Elachiptera

1. Thorax black................................................................................................................................................2

- Thorax entirely or mostly yellow................................................................................................................4

2. Wing with dark infuscations along R4+5 and CuA1 (Fig. 6) ............................................................. E. fucosa

- Wing hyaline................................................................................................................................................3

3 Frontal triangle short, half to two-thirds length of frons; arista strongly tapering, slender in distal third (Fig. 2) ................................................................................................................................. E. coniotrigona

- Frontal triangle reaching or almost reaching anterior margin of frons; arista broad to apex (Fig. 26) ......... ............................................................................................................................................. E. sacculicornis

4. Gena 0.25 times eye height ...............................................................................................................E. sp. A

- Gena 0.1–0.15 times eye height...................................................................................................................5

5. Scutum entirely yellow along dorsocentral lines.........................................................................................6

- Scutum with black dorsocentral lines, tapering posteriorly.........................................................................7

6. Arista parallel-sided almost to tip (Fig. 12); male surstylus as in Fig. 15 .............................. E. melinifrons

- Arista tapering in distal half, very slender at tip (Fig. 22); male surstylus as in Fig. 25 ............... E. rubida

7. Arista strongly tapering distally, very slender on distal fourth (as in Fig. 2); male surstylus evenly recurved ..................................................................................................................................... E. attenuata

- Arista evenly tapering to tip (Fig. 18); male surstylus long, straight and narrow (Fig. 21) .... E. queposana