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Prionopelta HNS sp.
Chiapas, soil. Dr. Goodnight's specimens could not with certainty be referred to any of the species named in the "Wheeler Collection. This genus, while small, seems greatly in need of revision. Phylogenetically, it has been related by Wheeler and Emery to the Ectatommini HNS . I would place it closer to the Amblyoponini HNS , and provisionally include it in the latter tribe. It has "amblyoponine teeth" at the sides of the head anteriorly, and several species have the anterior clypeal margin denticulate as in Amblyopone HNS . The structure of the alitrunk and especially the petiole also point to such a relationship. The mandibles seem only relatively slightly modified from certain types seen today among the amblyoponines.
A small, headless male specimen in the Wheeler Collection among unidentified miscellany, bearing Wheeler's handwritten label " Prionopelta HNS ," is probably correctly placed. The structure of the petiole and sculpture and pilosity are those of the worker. The venation in this specimen is unusually complete for such a small ant, and is further unusual in that Mf1 comes off well basad of cu-a.
In a recent paper (Brown and Nutting, 1950, pp. 116-121 and plate 8) it was stated that such basal displacement of the origin of Mf1 was more primitive than was an origin of this vein lined up with cu-a or apicad of cu-a. In a recent conversation, Dr. J. C. Bradley pointed out to me that this interpretation is questionable and cited examples in the Vespidae HNS and other aculeate groups to prove his point. I had originally arrived at the conclusion cited in our wing venation paper through study of certain drawings by H. II. Ross of primitive sawfly wings, referred to in the homologization on the first few pages of our paper.
In Dr. Bradley's opinion, these primitive sawfly wings just happen to be specialized in origin of Mf1. I am now willing to admit that in the ants, at least, basal displacement of this vein is probably derived. The true primitive position would then be the lining-up with cu-a, which checks with other primitive features as found in many myrmeciines and amblyoponines. The most important change this would make in our conclusions concerns the Dorylinae, which would seem to have arisen from within or near the amblyoponine stock instead of having arisen, as we stated in the paper in question, from a "pre-ponerine" stock. We most emphatically stand, however, on our conclusion that the cerapachyines cannot be considered as in the line of descent of the dorylines; the evidence of the wings and thorax shows that these two stocks are basically divergent. Prionopelta HNS is an amblyoponine (or very close relative) with definite "doryline tendencies'' in the venation of the forewing.
It may be mentioned here, in connection with the discussion of ant wing venation, that both Dr. J. C. Bradley and Dr. R. M. Schuster have communicated to me their belief that the vein we called "Rsx" in our wing venation paper cited above, the same element known as the "spurious vein" by mutillid specialists, is a secondary development in both ants and mutilloid wasps forming at the bending of certain crossveins such as the second or third r-m. This interpretation seems reasonable to me, especially in the light of Schuster's recent (1949, pp. 69-75, pl. 13, fig. 9) discovery of the very primitive mutillid Prototilla HNS , which lacks the spurious vein.
Returning to Prionopelta HNS and relatives, the genera Onychomyrmex HNS Emery, Lithomyrmex Clark HNS , and Examblyopone HNS Donisthorpe, which have been separated chiefly on the condition of the spurs of the middle and hind tibiae, must in my opinion also be included in the Amblyoponini HNS despite present classifications which place them in separate tribes. Onychomyrmex HNS ( O. hedleyi Emery HNS , O. mjobergi HNS Forel, O. doddi Wheeler HNS ) in the Wheeler Collection actually possess very small rudimentary spurs. These genera, with Prionopelta HNS , represent a developmental series with regard to the spurs of such continuity that it becomes evident that such a character in the Ponerinae may be accepted as of no more than generic significance. The same applies to the spurs in some ponerine tribes other than the Amblyoponini HNS , as will be seen under Belonopelta HNS below.