Key to the Mexican species of Olbiogaster Osten Sacken

Olbiogaster mexicana Lane & d'Andretta is only known from females. Regarding Olbiogaster sackeni Edwards and O. taeniata (Bellardi) the description of females included some characteristics indicated in the key of Lane & d'Andretta (1958: 514). Peterson (1981) added some illustrations of the wing, thorax, tarsomere and claw of Olbiogaster sackeni Edwards.

1. Male................................................................................................ 2 - Female.............................................................................................. 6 2(1). Front coxa yellow...................................................................... O. sackeni Edwards

- Front coxa dark brown................................................................................. 3

3(2). Hind femur dark brown with basal or distal yellow ring....................................................... 4

- Hind femur completely dark brown (Fig. 9C).................................................... O. puuc sp. nov.

4(3). Mesonotum with a dark brown central stripe, surrounded U-shaped black stripe (Fig. 2C); sternite 10 with elongated slender arms, apically with a long spine, curved (Fig. 6J)................................................ O. nuxco sp. nov.

- Mesonotum with different pattern; sternite 10 with elongated slender arms, apically with spine, slightly curved or a few setae5

5(4). Hind femur basal and apical 1/3 dark, middle 1/3 yellow; sternite 10 with elongated slender arms, apically not widened (Fig. 6D).................................................................................. O. halffteri sp. nov.

- Hind femur dark, except for yellow apex; sternite 10 with elongated slender arms, apically enlarged.... O. taeniata (Bellardi)

6(1). Coxae mostly blackish brown; hind femur entirely yellowish.......................... O. mexicana Lane & d´Andretta

- Fore and midcoxae yellow, with dark brown tinge; hind coxae dark brown; hind femur dark, except for basal 2/3 yellow ring (Fig. 7C)............................................................................... O. nuxco sp. nov.