Description of a new genus of primitive ants from Canadian amber, with the study of relationships between stem- and crown-group ants (Hymenoptera: Formicidae) Author Borysenko, Leonid H. text Insecta Mundi 2017 2017-08-11 2017 570 1 57 journal article 10.5281/zenodo.5169084 1942-1354 5169084 C6CCDDD5-9D09-4E8B-B056-A8095AA1367D Tribe Haidomyrmecini Bolton, 2003 Diagnosis (workers, gynes). (1) head capsule specialized: face and genae concave, clypeus modified (putative apomorphy); (2) mandibles long, scythe or L-shaped (putative apomorphy); (3) anterolateral clypeal margins not produced over mandibular bases in rounded lobes; (4) peg-like setae on anterior clypeal margin absent; (5) ocelli present or not; (6) relative length of antennomeres variable; (7) terminal flagellomere elongated or not; (8) neck long; (9) petiole pedunculate; (10) gastral constriction present or not. Comment. Under the PhyloCode, the taxon should be named “ Haidomyrmecini P , converted clade name” and defined as “the clade consisting of Haidomyrmex cerberus Dlussky, 1996 and all species that share a more recent common ancestor with Haidomyrmex cerberus Dlussky, 1996 than with Sphecomyrma freyi Wilson and Brown, 1967 or Zigrasimecia Barden and Grimaldi, 2013 ”. Composition. Genera Haidomyrmex Dlussky, 1996 ( type genus), Haidomyrmodes Perrichot, Nel, Néraudeau, Lacau, Guyotet, 2008 , Haidoterminus McKellar, Glasier and Engel, 2013 , Ceratomyrmex Perrichot, Wang and Engel, 2016 . Discussion. This group is morphologically compact, and readily distinguishable from the other stem taxa. The unique head and mandibles are the most important morphological features, but some findings from the statistical analysis are also noteworthy. The scape indices as well as the index F1L/ HL occupy an intermediate position between the Sphecomyrmini and crown-group ants. This negatively influenced the discrimination between stem- and crown-group ants in the canonical discriminant analysis, as well as limits the potential of antennal metrics for providing a more rigorous diagnosis of Pan-Formicidae P . All the other indices are statistically similar to those of the Sphecomyrmini . Unlike the Sphecomyrmini , there is no pattern F1L>P<F2L (many exceptions); however, some patterns in a F1-to-F2 ratio can be noted at the generic level: Haidomyrmex - F2L>F1L, Haidomyrmodes - F2L=F1L, Haidoterminus and Ceratomyrmex - F1L>F 2L. The presence of the gastral constriction in the Haidomyrmecini is questionable. Haidomyrmodes has been described with the gastral constriction, but it may be an artifact of preservation. It is also possible that this character is variable at the generic level, as in the Sphecomyrmini .