Thrincostoma [!] (Diagonozus) lettow-vorbecki Blüthgen, 1930: 497, 499, 503, 522, 536, MMM, FFF. Male holotype : R.D. Congo, Barumbu, 12.XI.1913, sur fleurs de Costus n°1169, leg. Dr. Bequaert (RMCA).
Thrinchostoma (Diagonozus) lettow-vorbecki Blüthgen: Michener 1978: 525.
Thrinchostoma lettow-vorbecki Blüthgen: Cockerell 1933: 24.
Thrinchostoma (Diagonozus) lettowvorbecki (Blüthgen): Pauly 1999: 156, 174.

Thrincostoma [!] (Diagonozus) guineense Blüthgen 1930: 536, MMM. Male holotype : Equatorial Guinea «(“Spanish Guinea”), Uelleburg, Benitogebiet, 1-14.II.1907, leg. Tessmann (MNHUB).
Thrinchostoma (Diagonozus) guineensis Blüthgen : Michener 1978 : 525 ; Pauly, 1999 : 156, 173.

Thrinchostoma (Diagonozus) ghesquieri Cockerell, 1933: 24, MMM. Male holotype: R.D. Congo, Yangambi, I.1925, leg. Lt. J. Ghesquière (RMCA). Michener 1978: 525; Pauly 1999: 156, 173, syn.; Michener 2000: 374.

Note: According to Blüthgen, T. guineensis may be simply a variety of T. lettowvorbecki so we preferred to place it in synonymy because the differences are minimal.