Prionopelta Mayr, 1866

Ladino, Natalia & Feitosa, Rodrigo M., 2020, Taxonomic revision of the genus Prionopelta Mayr, 1866 (Formicidae: Amblyoponinae) for the Neotropical region, Zootaxa 4821 (2), pp. 201-249 : 204-206

Prionopelta Mayr, 1866

Prionopelta Mayr, 1866: 503 (queen). Type-species: Prionopelta punctulata , by monotypy.

Prionopelta in Ponerinae: Dalla-Torre, 1893: 15.

Prionopelta in Amblyoponinae : Forel, 1893: 162; Forel, 1895:110 [Amblyoponeridae].

Prionopelta in Ponerinae, Proceratiini: Ashmead, 1905: 382.

Prionopelta in Ponerinae, Ectatommini: Emery, 1911: 32 [subtribe Typhlomyrmecini ]; Forel, 1917: 236; Wheeler, 1922: 642.

Prionopelta in Ponerinae, Amblyoponini : Kusnezov, 1955: 275 [subtribe Ericapeltini ]; Emery 1895: 766; Wheeler, 1910: 134; Brown, 1953: 11; Brown, 1960:173.

Prionopelta in Amblyoponinae , Amblyoponini : Bolton, 2003: 42, 156; all subsequent authors.

Junior synonyms:

Concoctio Brown, 1974 . Synonymy by Ward & Fisher, 2016: 691.

Examblyopone Donisthorpe, 1949 . Synonymy by Brown, 1951: 102.

Renea Donisthorpe, 1947 . Synonymy by Brown, 1953: 11.

Genus references ( Bolton, 2020): Dalla-Torre, 1893: 15 (catalogue); Forel, 1909: 242 (New World species key); Emery, 1911: 32 (diagnosis, catalogue); Chapman & Capco, 1951: 26 (Asia checklist); Wilson, 1958: 146 (Melanesia species key); Brown, 1960: 173, 218, 221 (review of genus, Neotropical species key, Indo-Australian species key); Kempf, 1972: 210 (Neotropical catalogue); Smith, 1979: 1335 (North America catalogue); Taylor & Brown, 1985: 39 ( Australia catalogue); Taylor, 1987: 64 ( Australia & New Caledonia checklist); Bolton, 1995a: 1052 (census); Bolton, 1995b: 364 (catalogue); Shattuck, 1999: 201 ( Australia synopsis); Shattuck, 2008: 22 (Indo-Pacific species revision, key); Arias-Penna, 2008: 48 (Neotropical species key); Yoshimura & Fisher, 2012: 16 (male diagnosis); Overson & Fisher, 2015: (Malagasy species revision, key); Fisher & Bolton, 2016: (guide to Malagasy genera); Cantone, 2017: 106 (brief male diagnosis); Fernández, Delsinne & Arias-Penna, 2019:501 (Neotropical species key).

Genus diagnosis (New World species). Monomorphic amblyoponine ants. Body covered by punctulate, punctate and foveolate sculpturing, except for the smooth mandible, antenna, legs and propodeal declivity; integument entirely covered by pubescence and flexuous setae. Mandible tridentate, short and adjacent to clypeus when closed. Clypeus convex and anteriorly with a row of tooth-like stout setae, the surfaces of which are carinate (only visible under SEM images). Antennomeres 1–4 forming a club. Petiole broadly attached to gaster.

Worker description. Small-sized ants (TL 1.23–1.76mm). Color pale-yellow to light brown. Integument thick, shiny and sculptured on head, mesosoma, petiole and gaster; surface of tooth-like setae of the anterior clypeal margin carinate; body with point-like sculpture that varies in size, depth and density and is more distinct on head dorsum, particularly on the lateral portion of frons; ventral portion of katepisternum weakly reticulate/aerolate; ventral portion of metapleuron weakly reticulate/imbricate. Body with three kinds of pilosity: pubescence, short setae, and long setae; pubescence converging to center/median line of sclerites, more obvious on head dorsum, pronotum and first gastral tergite; long setae almost of same length as antennomeres 1–2 together; short setae as long as preapical antennomere; in full-face view, mandible with short and long setae; dorsal and ventral surface of mandible with at least eight sparse, long and flexible setae each; anterior portion of the median area of clypeus with a pair of long flexible setae directed anteriorly; midportion of the clypeal median area with a pair of long flexible setae directed dorsally; posterior portion of the median area of clypeus with one long flexible seta directed dorsally; antenna pubescent, scape with short erect setae; head dorsum and mesosoma pubescent; pronotum with short, erect and dispersed setae; mesonotum and propodeum with sparse, erect and long setae; propodeal declivitous face devoid of pilosity; petiolar node with some erect and long setae; subpetiolar process with one or two long posteriorly curved setae.

Head as long as or slightly longer than broad, lateral margins slightly convex, smoothly converging anteriorly; posterior corners convex; posterior margin weakly concave. Mandible subtriangular, short and adjacent to the anterior clypeal margin when closed; basal margin convex or straight; masticatory margin tridentate; apical tooth longest, size proportion between basal and median tooth variable, diastema between basal and median tooth longer than between the latter and the apical tooth. Anterior clypeal margin rounded or with median portion projecting anteriorly; anterolateral margin sinuate; medial carina not reaching the anterior margin; tooth-like stout setae slightly directed anterolaterally, apparently rising from the anterior clypeal margin and (1) under a clypeal lamella that varies in length or (2) welded along this lamella. Palp formula 2:2. Frontal lobe small, approximated, partially covering the antennal socket. Eleven or twelve antennomeres; antennomeres 1–4 forming a club, each one separated from the other by shallow to deep constrictions; scape elongate and uniform until half of its length, then slightly thick and curved at apex; scape not reaching the posterior margin of head. Compound eye reduced, set laterally at or immediately posterior to the head midlength. Postgenal suture present and complete, extending towards posterior margin; in ventral view, median portion of the occipital margin of head concave.

Mesosoma unarmed. Dorsal profile evenly convex, interrupted only by the promesonotal suture and the metanotal groove. Dorsum of pronotum with anterior margin convex, lateral margin slightly converging to the promesonotal suture. Dorsum of mesonotum trapezoidal; ventral portion of katepisternum at lower level than adjacent surface. Propodeal spiracle small and directed ventrolaterally. Propodeal declivity slightly inclined posteriorly; ventral surface medially projected as an inconspicuous tubercle. Posteroventral propodeal lobe conspicuous (character 67 of Keller [2011]). Metapleural gland orifice opening posteriorly; ventral flap on the metapleural gland opening conspicuous (character 61 of Keller [2011]). Legs relatively short and robust with tarsal claws small and simple. Foreleg with large and rounded coxa; trochanter conspicuous and rounded; femur and tibia thickened; posterior face of the basitarsi with pronounced notch; four basal tarsomeres with a row of small and acute projections on the internal surface. Mid- and hindcoxae with a pair of longitudinal carinae on the dorsal surface; femur and tibia of midleg and hindleg more slender than in foreleg. Tibia of the midleg with a vestigial spur; hindleg with a pectinate spur; posterior face of the basitarsus notched.

Petiole not pedunculated, node well developed. In dorsal view, anteroventral portion of the petiolar tergite anterior to the petiolar spiracle projected as a lateral carina (character 97 of Keller [2011]); lateral margin rounded. Spiracle small and rounded in profile; dorsal profile slightly and uniformly convex. Subpetiolar process conspicuous. Posteroventral angle of process mainly obtuse; anterior and posterior margins parallel or converging apically; posterior margin concave or straight; fenestra present. Petiolar sternite triangular, with rounded corners in ventral view; visible part of helcium rounded. Gaster elongate; prora present as a rounded anterolateral projection. Anterior face of first gastral sternite slightly concave between projections of prora. Deep girdling constriction of second gastral segment present. Sting apparatus well developed.

Queen description. Slightly larger than workers (TL 1.56–2.11mm). Morphologically similar to workers, with mesosoma well-developed.

Head with compound eyes large, placed at midlength of head; three well-developed ocelli arranged in an equilateral triangle, similar in size.

Pronotal lobe small. Mesoscutum large and trapezoidal; promesonotal suture uniformly continuous in dorsal view; notauli incomplete when present; parapsidal lines and parascutellar carina present; tegulae and axillae flattened. Mesoscutellar disc at the same level of the mesoscutum; rounded. Mesosoma uniformly convex in lateral view. Oblique mesopleural sulcus incomplete, mesopleural pit conspicuous; spiracular sclerite subtriangular. Fullywinged forms. Wing venation as in Yoshimura & Fisher (2012): “Forewing with a small stigma, radial sector absent between M+Rs and 2r-rs, radial sector reaching the costal margin, 2r-rs connected with radial sector distal to pterostigma, 2rs-m present, cu-a located far from junction between media and cubitus; hindwing with radius present, 1 rs-m present, media present apical to 1rs-m”. Four submedian hamuli present.

Petiole and subpetiolar process similar to those of workers; gaster elongated and robust.

Male description. Small to medium-sized (TL 1.60–2.00 mm). Color dark-yellow to brownish-black. Sculpture and pilosity traits similar to those of workers. With well-developed mesosoma.

Head rounded. Posterior margin convex or slightly concave at its median portion; posterior corners convex. Mandible subfalcate; bidentate; apical tooth the longest. Clypeus with anterior margin projecting medially or evenly rounded; frontoclypeal suture smoothly converging to the frons with its median portion truncate or evenly rounded. Thirteen antennomeres; scape short. Compound eye large, occupying almost a quarter of head and set laterally, near to the frontoclypeal suture; three well developed ocelli present and similar in size.

Mesosoma and wings similar to those of queens, complete notaulus always present.

Petiolar node with anterior margin distinctly inclined posteriorly in profile; subpetiolar process with posteroventral margin straight. Gaster elongate and slender. Girdling constriction of the second gastral segment present and shallow.

Etymology. Although not specified in the original description, the name refers to the combination of the row of tooth-like stout setae and the shape of the clypeus. From Greek, príon: saw and pelta: shield ( Wheeler & Wheeler 1984).

Comments. Prionopelta mocsaryi Forel, 1907 , was excluded from this revision. It was described from a specimen putatively from Paraguay but it is actually a mislabeled specimen of Prionopelta opaca Emery, 1897 , a Melanesian species ( Wilson 1958; Brown 1960). Prionopelta mocsaryi is currently a junior synonym of P. opaca ( Bolton 2020) . We confirmed the synonymy through the examination of images of the relevant types at AntWeb.org.

Workers and queens of the Neotropical species always have a well-impressed metanotal groove and 11 or 12 antennomeres, while some Old World species can have the metanotal groove indistinct, and fewer than 11 antennomeres ( Brown 1960; Arias-Penna 2008; Fernández et al. 2019). The worker caste shares a small body size; punctulate, punctate or foveolate sculpturing that is more conspicuous on the head dorsum; erect setae; abundant pubescence; a small genal tooth; and a reduced compound eye. The carinate surface of each tooth-like clypeal seta is clearly noticeable in the images available for the specimen ANTWEB 1008581 in AntWeb.org.

A detailed morphological description of the larvae was provided by Wheeler & Wheeler (1952), based on five larvae and two “semipupae” from Colombia. The authors identified the specimens as P. punctulata , but we suspect they were misidentified and could have been specimens of Prionopelta antillana . We were not able to locate these specimens.

Distribution. Neotropical Prionopelta species range from the central portion of USA state of Florida, the Caribbean Islands and Mexico to northwestern Argentina.