Basiceros redux ( Donisthorpe 1939 ) A taxonomic revision of the dirt ants, Basiceros Schulz, 1906 (Hymenoptera, Formicidae) Probst, Rodolfo Da Silva Brandão, Carlos Roberto Ferreira Zootaxa 2022 2022-06-02 5149 1 1 75 Probst & Brandão 2022 Probst & Brandão 2022 [625,865,906,933] Insecta Formicidae Octostruma Animalia Hymenoptera 68 69 Arthropoda species reducta comb. nov.      Basiceros redux( Donisthorpe 1939)=  ( Fig 29)  Type-material: holotype(male), Donisthorpe 1939: 152, GUYANA. Type-locality: Guyana(“ British Guiana”): Kaieteur Savannah, 5.ix.1937(O.W. Richards) (MNH1014339) (examined).  Incertae sedisin  Rhopalothrix: Brown & Kempf, 1960: 164. Combination in  Basiceros: Bolton1995: 80. Status as species: Kempf 1972: 227; Bolton1995: 80.   Comments. Brown & Kempf (1960), while mentioning the taxonomic uncertainty regarding  Basiceros-genus group males, added that  Rhopalothrix reduxcould be placed in  Eurhopalothrix,  Rhopalothrix,  Octostruma, or  Talaridris. Few are the species from the  Basiceros-genus group in which the males are known, making it hard to address intraspecific variation. Despite the holotypeconditions, a detailed examination revealed unique features present of  Basiceros reduxwhen compared to other “basicerotine” males: 1. Mandibles—shape and dentition: most  Basicerosmales have mandibles somewhat elongate, with the external margin apically curved and 9-14 teeth on the masticatory margin. In  Basiceros redux, the mandibles are triangular, having seven or eight teeth; 2. Head shape:  Basicerosmales have an anteriorly elongated head (the overall head shape has a piriform to subpiriform aspect) and the occipital margin projected and carinate, forming a neck. In  B. reduxthe head is rounded and the occipital margin lacks a neck; 3. Antennae: antennomeres of  B. reduxare subequal from A3 to the apical segment, a condition not observed in any  Basicerosmale examined for this study; 4. Ocelli: in general,  Basicerosmales have the ocelli arranged on the top of the head, surrounded by a conspicuous cephalic crest. In  B. redux, although the ocelli are located on the top of the head, the crest is absent; 5. Mesosoma: in  B. reduxthe posterior face of mesoscutellum is strongly truncated and the metanotal band is extremely reduced, giving the mesoscutum + mesoscutellum set an aspect of plateau. In  Basicerosmales, the posterior margin of mesoscutellum is rounded and the metanotum, although reduced, is detached from the mesoscutellum; 6. Petiolar node in dorsal view: for  Basicerosmales is elongated, longitudinally rectangular. In  B. reduxand the known males of  Octostruma,  Rhopalothrix, and  Eurhopalothrix, the node is transversally rectangular; 7. Postpetiolar node in dorsal view: in  Basicerosmales is nodiform and subglobular, conditions not observed for  B. redux; 8. Gastral integument: in opposition to the shiny integument and the sparse pilosity found in  B. redux, males of  Basicerospossess finely punctuate to reticulate integument and a more abundant pilosity; 9. Propodeal projections:  Basicerosmales have short projections, sometimes angled. In  B. reduxthe propodeum is armed with a well-developed triangular and lamelliform projection, similar to observed for  Octostrumamales; 10. Forewing venation: in  B. reduxthe vein M+Cu has a spectral basal portion, similarly to observed for  Octostrumamales, whereas in  Basicerosmales that vein is invariably complete.  Eurhopalothrixmales tend to have M+Cu completely spectral; 11. Forewing venation II: submarginal cell 1: known  Rhopalothrixmales have the submarginal cell 1 open (for  Eurhopalothrixmales, the Rs+M vein is in general spectral or slightly tubular, and a close observation shows that it closes the submarginal cell 1) and the veins Rs, M, Cu, and A nebular or spectral in their basal half (similar condition observed for examined  Eurhopalothrixmales). This set of characteristics are absent in  B. redux, with the male having a submarginal cell 1 closed, feature shared by  Basicerosand  Octostrumamales. Additionally,  B. reduxpresents another configuration for other veins above cited; 12. Pterostigma:  Eurhopalothrixmales lack the pterostigma or it is poorly developed. Both  Basicerosand  Octostrumashare a conspicuous pterostigma (for the latter, in some males it can be slightly narrower and not greatly developed); 13. Tegula: in  B. reduxthe tegulae are round, contrasting with other  Basicerosmales, where they are subrectangular and with the posterior margin convex;  Dietz (2004: 151)also proposed transferring  B. reduxto  Octostrumabased on wing features. In addition, Dietz suggested that  B. reduxcould be a male of  O. iheringi, based on the pilosities of the petiolar peduncle and ventral face of the postpetiole. However, the current knowledge of  Octostrumamales is considerably scarce, therefore preventing a correct association of  Basiceros reduxto a valid  Octostrumataxon. 4029332380 [151,836,1011,1035] Guyana GUYANA 68 69 1 holotype