Key to the species of the subgenus Liphanthus s. str. (modified from Ruz & Toro, 1983). 1 Males ............................................................................................................................................................2 - Females........................................................................................................................................................6 2 Laterodistal margin of clypeus in frontal view strongly concave................................................................3 - Laterodistal margin of clypeus in frontal view almost straight...................................................................4 3 Flagellum gradually enlarged distally. Apical margin of labrum in frontal view concave............................ ................................................................................................................................ L. barbatus Ruz & Toro 3 Flagellum not enlarged distally. Apical margin of the labrum in frontal view convex ................................ ............................................................................................................................... L. nigriceps new species 4 Flagellar segments longer than broad, last one about 2.5 times longer than broad....................................... ............................................................................................................................ L. brevicornis Ruz & Toro - Flagellar segments about twice as long as broad or more, last one three or more times as long as broad 5 5 Last flagellomere distally about half as broad as median segments, strongly curved. Scape with yellow spot ................................................................................................................................... L. sabulosus Reed - Last flagellomere about as broad as median segments, almost straight. Scape without yellow spot............ ........................................................................................................................... L. chillanensis Ruz & Toro 6 Second submarginal cell with anterior margin about as long as posterior or slightly shorter.....................7 - Second submarginal cell with anterior margin distinctly shorter than posterior ........................................ 8 7 Marginal cell generally longer than (or similar in length to) distance from apex to wing tip. Paraocular area with yellow spot, extending ventrally to level of tentorial pit or slightly below it. L. sabulosus Reed - Marginal cell shorter than distance from apex to wing tip. Paraocular area without yellow spot................. ............................................................................................................................... L. nigriceps new species 8 Integument of mesosoma almost smooth. Facial fovea sinuous, widened ventrally .................................... ............................................................................................................................ L. brevicornis Ruz & Toro - Integument of the mesosoma strongly areolate. Facial fovea almost straight, not widened ventrally........9 9 Facial fovea subparallel to inner orbit. Clypeus three times as broad as long. Outer surface of mid basitarsus with small basal yellow spot ............................................................................. L. barbatus Ruz & Toro - Facial fovea ventrally farther from inner orbit than dorsally. Clypeus less than three times as broad as long. Outer surface of mid basitarsus with large yellow area extending beyond middle ............................. ........................................................................................................................... L. chillanensis Ruz & Toro

Published as part of Vivallo, Felipe, 2008, Liphanthus Reed, 1894 (Hymenoptera, Andrenidae, Protandrenini): Two new Argentine species and keys to the species of the subgenera Liphanthus s. str. and Melaliphanthus Ruz & Toro, 1983, pp. 55-62 in Zootaxa 1854 on pages 60-61, DOI: 10.5281/zenodo.274439