[38] A. horridus is a distinctive, gracile, testaceous species with very long, slender, sparsely toothed mandibles. The type, an ergatoid queen, was collected by Karol Lenko during our joint 1962 trip in Brasilian Amazonia, but only one of the other samples taken by our group on that excursion was mentioned by Kempf in the original description. Additional samples are from Pará, near Belém: Pirelli Rubber Plantation, Iriboca (Brown). Reserva Guamá (P. Dias). Instituto Agronomico do Norte (F. G. Werner). Amazonas, N and E of Manaus: Manaus-Itacoatiara Highway (Ruta 1), km 49 (Brown). Reserva Ducke (Brown). All localities were in lowland rain forest. Workers were found singly in leaf litter, in or under a small rotten log, and in a small ne...