Strumigenys electrina

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Strumigenys electrina
Temporal range: Burdigalian, Early Miocene Dominican amber, Dominican Republic
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. electrina
Binomial name
Strumigenys electrina
De Andrade, 1994

Baroni Urbani & Andrade 1994-39Figure-24.jpg

Identification

A short mandibulate Strumigenys close to ohioensis and differing from it in several small characters, such as the teeth being subequal in size and the sculpture coarsely reticulate-punctuate on the legs and missing on the postpetiolar node. We already mentioned the close similarity between Strumi­ genys electrina and S. ohioensis KENNEDY & SCHRAMM. The differences between the two are small but numerous; at least the most important of them can be listed as fol­ lows: the teeth of electrina, subequal in size and without basal lamella vs. a basal lamella followed by irregular medial teeth in ohioensis; the infraspinal lamellae straight in profile in electrina and concave in ohioensis; the pronotum simply reticu­ late in electrina and irregularly rugose in ohioensis; legs deeply reticulate in electrina and simply punctate in ohioensis; the postpetiolar node smooth in electrina and sculptured in ohioensis; clypeal piliferous tubercles absent in electrina and present in ohioensis; presence of pairs of long cephalic, thoracic, and gastral hairs in electrina vs. their smaller number and different distribution in ohioensis; presence of spatulate hairs on the clypeal sides of electrina vs. ]-shaped hairs in ohioensis. S. ohioensis is reported from soil samples from several states of the U. S. A. inclu­ ding Alabama, Arkansas, Delaware, Illinois, Louisiana, Maryland, North Carolina, Ohio, Tennessee, and Virginia. According to BROWN (1953) ohioensis is not particu­ larly related to any other known species and S. electrina is likely to represent its sister species. If electrina had not been described from Dominican amber, then from its morphology alone, one could easily have supposed provenance from the southern United States.

Distribution

This taxon was described from Dominican amber, Dominican Republic (Burdigalian, Early Miocene).

Castes

Nomenclature

  • *electrina. *Strumigenys electrina De Andrade, in Baroni Urbani & De Andrade, 1994: 38, figs. 17, 18, 24, 25 (w.) DOMINICAN AMBER (Miocene). Combination in Smithistruma: Bolton, 1995b: 384; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 119.

Holotype: Staatliches Museum fur Naturkunde Stuttgart, no. DO-3854-1.

Description

Worker (Fig. 24). Measurements (in mm) and indices: total length (mandibles included) holotype 1.88, paratypes 1.84 - 1.88; HL holotype 0.44, paratypes 0.40 - 0.44; HW holotype 0.32, paratypes 0.32 - 0.36; SL holotype and paratypes 0.20; ML holotype and paratypes 0.12; AL holotype and paratypes 0.48; PW holotype and paratypes 0.16; petiole length holo­ type and paratypes 0.20; petiole maximum width holotype and paratypes 0.08; postpetiole maximum width holotype and paratypes 0.12; gaster maximum width holotype and paratypes 0.28. CI holotype 72.7, paratypes 72.7 - 90.0; SI holotype 62.5, paratypes 55.5 - 62.5; MI holotype 27.3, paratypes 27.3 - 30; SMI holotype and paratypes 166.6.

Description. - Head (Fig. 25) with anteriorly converging and posteriorly rounded sides; occipital concavity normally impressed. Preocular laminae straight. Clypeus slightly longer than broad, with convex sides converging anteriorly and the posterior margin medially angulate. Scapes 1h of head length, short, broad, flattened, but only slightly bent close to the base; their broadest point about at mid length; their external border irregularly convex, the internal border nearly straight. Last funicular joint longer than the rest of the funiculus. Mandibles short, less than l /4 of head length, narrow and with the shape of an elongated triangle; inner mandibular border without visible basal lamella but with a toothless space followed by a series of 11 acute denticles only slightly decreasing in size from the base to the apex. Labrum with a visible pair of anteriorly projecting lobes.

Trunk essentially flattened on the dorsum, with a small pronotal declivity in front; propodeal suture invisible; humeral angles poorly marked and continuing post­eriorly in an edge leading to the propodeal spines; propodeal spines short, stout, directed backwards and slightly upwards.

Spongiform processes well developed, covering the sides of the petiolar and post­ petiolar nodes, and extending over the whole articulation of the latter with the gaster; on both peduncular nodes the spongiform processes extend laterally in a pair of short lateral wings and ventrally in a long, median process. A pair of transparent infraspinal lamellae run straight between the propodeal spines and the ventral post­ erior border of the trunk.

Gaster oval and not anteriorly truncated in dorsal view.

Sculpture: cephalic dorsum, trunk and legs covered with coarse reticulation, more superficial on the anterior half of the head, trochanters, femora, and tibiae and nearly effaced on the clypeus and on the scapes; mandibles and funiculi punctuate only; very evident smooth areas on the mesopleurae and on the postpetiolar node; anterior portion of the first gastral tergite strongly costulate.

Pilosity: dorsum of the head with sparse, suberect spatulate hairs slightly longer on the sides of the clypeus; a row of similar, longer, hairs on the anterior border of the clypeus; minute, appressed, simple hairs on the mandibles and the funiculi and the legs; two pairs of erect, slightly spatulate setae on the vertical area and a pair of standing setae twice as long protrude from behind the antennal scrobes; pronotum with a pair of very long, feebly spatulate setae close to its anterior border and another pair of slightly shorter, normally acuminate setae on the promesonotal suture; 1-2 pairs of similar setae on the abdominal segments; pairs of shorter, similar setae on the ventral part of the gastral segments.

Colour uniformly ochraceus feebly shining.

References

  • Baroni Urbani, C. & De Andrade, M.L. 2007. The ant tribe Dacetini: limits and constituent genera, with descriptions of new species. Annali del Museo Civico di Storia Naturale “G. Doria” 99: 1-191.
  • Bolton, B. 1995b. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 384, combination in Smithistruma, in catalogue)
  • Bolton, B. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). J. Nat. Hist. 3 33: 1639-1689 (page 1673, combination in Pyramica)
  • Bolton, B. 2000. The ant tribe Dacetini. Mem. Am. Entomol. Inst. 65: 1-1028 (page 246, catalogue)
  • De Andrade, M. L. 1994a. [Untitled. Strumigenys electrina de Andrade n. sp.] Pp. 38-41 in: Baroni Urbani, C., De Andrade, M. L. First description of fossil Dacetini ants with a critical analysis of the current classification of the tribe (Amber Collecti (page 38, figs. 17, 18, 24, 25 worker described)