Key to the species of Robertsia

a

b

c

1A

Head extremely narrow, 2.3 - 2.5 times longer than wide across the compound eyes (figs. a & b); fore tibial armature consisting of two sub-parallel rows of six to eight teeth, converging proximally (fig. c).

a

b

c

1B

Head less elongate, at most 1.9 times longer than wide (figs. a & b); fore tibial armature a single row of four to seven teeth (fig. c).

a

b

c

2A

Clypeal margin slightly concave with small medial point (fig. a); head distinctly tapering anteriorly (fig. b); shortest dorsal distance between eyes less (0.75X) than eye length (fig. b); mandibles in close apposition at base (figs. a & b); vertex short: in lateral view 0.17X eye length (fig. c)

a

b

c

2B

Clypeal margin with quadrate medial protrusion (fig. a); head sub-parallel sided, only slightly tapering anteriorly (fig. b); shortest dorsal distance between eyes greater (1.15X) than eye length (fig. b); bases of mandibles widely spaced (figs. a & b); vertex longer: in lateral view 0.45X eye length (fig. c).

a

b

c

3A

Mandibles smooth, tusk-like, extending away from the clypeal margin (figs. a & b); clypeal margin smooth, broadly concave (fig. a); inter-antennal carina not extending forward beyond toruli (fig. a); head without conspicuous setae (figs. a & b); fore tibial armature arranged in semi-circle (fig. c); fore tibia short, 1.5X longer than wide, club-like (fig. c).

a

b

c

3B

Mandibles broad with a sub-apical tooth and two basal teeth on inner margin, held in close apposition with clypeal margin (fig. a); clypeal margin deeply concave with a medial tooth (fig. a); inter-antennal carina extends to clypeal margin (fig. a); head with conspicuous setae (figs. a & b); fore tibial armature in straight line at apex of tibia (fig. c); fore tibia elongate, 2.5 X longer than wide (fig. c).

a

b

1A

Pronotum 1.35–1.4X longer than wide (figs. a & b); propodeum at least 4X longer than mesonotum (figs.a & b); propodeal spiracles situated more than 1.5X their own diameter from anterior propodeal margin (figs. a & b).

a

b

1B

Pronotum less than 1.2X longer than wide (figs. a & b); propodeum medially at most 1.5X longer than mesonotum (figs. a & b); propodeal spiracles situated about their own diameter from anterior propodeal margin (figs. a & b).

a

2A

Head tapering anteriorly (fig. a); eyes large, eye length 1.3X longer than cheek length, almost half (0.47X) of head length (fig. a); mandibles short and in close apposition (fig.a); vertex concave (fig. a); clypeal margin with a sharp, small median tooth (fig. a).

a

2B

Head parallel sided (fig. a); eyes smaller, eye length only as long as cheek length, slightly more than a third (0.35X) of head length (fig. a); mandibles long and narrow, widely spaced (fig. a); vertex convex (fig. a); clypeal margin with a slight quadrate medial protrusion (fig. a).

a

b

3A

Mandibles smooth, tusk-like, widely spaced (fig. a); head and metosoma without conspicuous setae (figs. a & b); clypeal margin smooth, broadly concave (fig. a); inter-antennal carina not extending forward beyond toruli (fig. a); propodeal spiracles small, diameter c. a sixth of propodeal length (fig. b).

a

b 

3B

Mandibles broad with a subapical tooth and two basal teeth on inner margin, in close apposition (fig. a); head and metosoma with conspicuous setae (figs. a & b); clypeal margin deeply concave with a medial tooth; inter-antennal carina extends to clypeal margin (fig. a); propodeal spiracles large, diameter c. a third of propodeal length (fig. b).