Key to species of Tybalmia (adapted from Dillon & Dillon 1945)

1. Each elytron with two maculae behind middle, placed transversely. Ecuador, Peru, Brazil (Amazonas).................................................................................................... T. mydas (Lucas, 1859)

- Each elytron with only one macula behind middle........................................................... 2

2(1). Humerus with two tubercles. Colombia, Ecuador, Peru, Venezuela, Guyana, Suriname, French Guiana, Brazil (Amazonas, Pará)........................................................................... T. pupillata (Pascoe, 1859)

- Humerus with a single tubercle.......................................................................... 3

3(2). Dark elytral macula located behind middle V-shaped. Guatemala, Nicaragua, Costa Rica, Panama, Venezuela ................................................................................................. T. caeca Bates, 1872

- Dark elytral macula located behind middle not V-shaped, if V-shaped, then preceded by large yellowish-white pubescent macula.............................................................................................. 4

4(3). Vertex with one or two rounded dark spots on each side of median groove. Colombia .... T. breuningi Dillon & Dillon, 1952

- Vertex without rounded dark spots........................................................................ 5

5(4). Elytra with very large yellowish-white pubescent macula close to anterior margin of the dark macula behind middle (light macula reaching anterior quarter of the elytra). Mexico (Veracruz), Guatemala, Honduras, Costa Rica, Panama ............................................................................................. T. funeraria Bates, 1880

- Elytra without very large yellowish-white pubescent macula close to anterior margin of the dark macula behind middle (light pubescent macula, when present not reaching anterior quarter of the elytra)....................................... 6

6(5). Dark elytral macula behind middle not preceded by yellowish pubescent macula. Ecuador ............. T. diffusa sp. nov.

- Dark elytral macula behind middle preceded by yellowish pubescent macula...................................... 7

7(6). Yellowish elytral pubescent macula preceding dark macula with similar width. Panama ........ T. pixe Dillon & Dillon, 1945

- Yellowish elytral pubescent macula preceding dark macula about half width of dark macula. Panama ............................................................................................... T. ianthe Dillon & Dillon, 1945