Key to species of the P. ferrugineus group, based on the workers and queens This key incorporates the two new species into the previously published key for the P. ferrugineus group (Ward 1993: 131–132). The latter should be consulted for identification of the remaining species. Sample sizes are given for each set of measurements. 1 Eyes more elongate (worker REL 0.48–0.55, n = 22; queen REL 0.47–0.50, n = 4); profemur more robust (worker FI 0.42– 0.46, n = 22; queen FI 0.46–0.51, n = 4); worker metanotal groove weakly impressed; dead twig inhabitant............. 2 - Eyes less elongate (worker REL 0.39–0.50, n = 280; queen REL 0.38–0.48, n = 166); profemur more slender (worker FI 0.35– 0.41, n = 22; queen FI 0.39–0.44, n = 13); worker metanotal groove well developed; obligate inhabitants of swollen-thorn acacias (Fachellia species)................................. remaining species; see couplets 11–19 of key in Ward (1993) 2 Large species (worker HW 1.15–1.28, n = 14; queen HW 1.28, n = 1) with longer legs (worker LHT 0.91–1.00, n = 14; queen LHT 1.0 4, n = 1) and broader head (worker CI 1.01–1.05, n = 14; queen CI 0.88, n = 1); palp formula 4,3........... evitus - Smaller species (worker HW 0.94–0.99, n = 8; queen HW 1.01–1.06, n = 3) with shorter legs (worker LHT 0.73–0.77, n = 8; queen LHT 0.80–0.83, n = 3) and more elongate head (worker CI 0.90–0.94, n = 8; queen CI 0.85–0.86, n = 3); palp formula 5,3............................................................................................ feralis

Published as part of Ward, Philip S., 2017, A review of the Pseudomyrmex ferrugineus and Pseudomyrmex goeldii species groups: acacia-ants and relatives (Hymenoptera: Formicidae), pp. 524-542 in Zootaxa 4227 (4) on page 533, DOI: 10.11646/zootaxa.4227.4.3, http://zenodo.org/record/306006