Dinoponera gigantea

A soil nesting species with small colonies that average 41 workers.

Identification
Lenhart et al. (2013) - Worker. Dinoponera gigantea can be distinguished from other Dinoponera species by the following combination of character states: antero-inferior corner of pronotum with distinct tooth-like process; integument finely micro-sculptured and not shiny; drab pilosity notably dense, long and flagellate; scape length longer than head width; total body length over 30 mm. Dinoponera gigantea is the largest species in the genus reaching up to 3.6 cm total body length. Dinoponera gigantea can be separated from all but two species by the presence of a tooth-like process on the antero-inferior corner of the pronotum. Dinoponera lucida and Dinoponera australis have a tooth-like process on the pronotum, but are smaller (usually less than 30 mm). In addition D. lucida has a shiny integument and D. australis lacks the long, flagellate pubescence.

Male. Males of this species are easily recognized by their funiculus which is covered in long standing setae, shiny dark reddish brown integument and the combination of a long pygidial spine, volsella with two basal teeth, lobed end of digitus volsellaris and deep concavity on the side of the penis valve of the aedeagus.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Guyana, Peru.

Dinoponera gigantea has been found on the coast of Guyana, in the Brazilian states of Amazonas, Pará including Marajo Island, Mato Grosso and Maranhão as well as the Loreto Province in Perú. Dinoponera gigantea is reported to be common in un-flooded forests in the vicinity of Belém, Pará (Kempf 1971, Overal 1980). It is probable that D. gigantea is found in French Guyana, Suriname, Venezuela and southeastern Colombia because these regions are adjacent to known D. gigantea localities and have similar lowland rainforest habitat. However, no specimens from these nations are known to us, perhaps as a result of a lack of sampling or the range is absent from Colombia and southwestern Venezuela.

A record from Rio de Janeiro (from the ) is puzzling as it is disjunct from the known range of D. gigantea. The most southeastern locality for D. gigantea is over 1,480km to the nearest portion of the state of Rio de Janeiro. In addition, Rio de Janeiro is in a well collected area where no other Dinoponera have been found. The label reads ‘R.d.Janeiro, Brazil, D. Davis’ and the specimen agrees in all morphological characters with D. gigantea. This locality is omitted from the species’ range map because of its questionable nature. If other collections can validate this locality it would mean a significant range extension for D. gigantea. (Lenhart, Dash & Mackay, 2013.)

Nomenclature

 *  gigantea. Ponera gigantea Perty, 1833: 135, pl. 27, fig. 3 (w.) BRAZIL. Kempf, 1971: 372 (m.). Combination in Dinoponera: Roger, 1861a: 38. Senior synonym of grandis: Roger, 1861a: 38; Kempf, 1971: 371.
 * grandis. Ponera grandis Guérin-Méneville, 1838: 206 (w.) BRAZIL. Emery, 1911a: 219 (m.); Wheeler, G.C. & Wheeler, J. 1986a: 387 (l.). Combination in Dinoponera: Roger, 1861a: 38. Junior synonym of gigantea: Roger, 1861a: 38; Kempf, 1971: 371. See also: Haskins & Zahl, 1971: 1.

Worker
Lenhart et al. (2013) - (mm) (n=15) TBL: 31.62–36.02 (34.34); MDL: 4.59–5.35 (4.92); HL: 5.89–6.65 (6.31); HW: 5.74–6.27 (6.00); SL: 5.95–6.43 (6.30); WL: 8.71–9.94 (9.35); PL: 2.72–3.06 (2.81); PH: 3.08–3.67 (3.59); PW: 1.85–2.07 (1.98); GL: 9.43–12.24 (10.94); HFL: 8.10–9.3 (8.74).

A description of the external morphology of the worker is given in Kempf (1971): “Length of scape exceeding maximum width of head. Pubescence on front of head quite dense yet inconspicuous, not concealing the integument. Gular (ventral) surface of head reticulate-punctate throughout, very finely striate in front, the striae strongly converging mesad toward the anterior border. Sides of head reticulate-punctate, subopaque. Antero- inferior corner of pronotum dentate. Pronotal disc reticulate-punctate, subopaque, the paired swellings rather inconspicuous, but the median impression between swellings distinct, integument irregularly wrinkled. Tarsus I of hind leg longer than maximum head length. Petiole reticulate-punctate and subopaque, rectangular in profile, the anterior surface straight to slightly concave; the anterior upper corner more narrowly, the posterior corner more broadly rounded; posterior surface with the vertical sulcus always distinct; in dorsal view the petiole is decidedly longer than broad, width-length proportion below 0.80. Terga I and II of gaster opaque, sharply reticulate-punctate, densely foveolate (from each foveola arises a short decumbent hair), with scattered, bristle bearing, larger pints. The appressed pubescence, although inconspicuous, is densely spread over the entire terga, stridulatory file on acrotergite (portion of tergum that is normally concealed under the overlapping preceding tergum) of tergum II short, narrow, inconspicuous, not crossing beyond anterior half of acrotergite (hence not easily seen if entire acrotergite is not exposed).”

Male
Lenhart et al. (2013) - A description of the external morphology of the male is given in Kempf (1971). Measurements done by Kempf (1971) are included as only one male D. gigantea was examined by us while the measurements of Kempf (1971) most likely represent the means of the four males examined in that study: “Measurements in millimeters: total length 22.0; maximum length of head capsule 2.48; maximum width of head (eyes included) 3.10; maximum diameter of eyes 1.86; scape length 0.93; length of funicular articles I: 0.21, II: 1.86; Weber’s length of thorax 7.12; hind femur length 5.57; hind tarsus I length 5.38; petiole length 2.16, width 1.24, height 1.76; tergum I of gaster length 3.09, width 2.88; fore wing length 15.6; hind wing length 12.15. Chestnut brown, smooth and shining except funiculi, clypeus, front, tibiae and tarsi which are finely punctuate to reticulate-punctate; terga III and following of gaster weakly, superficially and finely reticulate. The entire insect covered with long, subdecumbent, silky pubescence, except funiculi where the pubescence is minute. Standing hairs long and abundant on body, lacking on mid-dorsum of terga II-V of gaster; long hairs on scapes rather numerous, length not much longer than twice the diameter of scape…Anterior border of labrum rounded, not visibly excised… Pygidial spine long and well developed. Parameres (gonostyli) of genitalia in side-view narrow and spear-pointed… Hypopygidium (subgenital plate of subandrium) apically rounded…”

Genitalia. Basal ring with wide dorso-anterior loop structures, dorsal depression on basal ring posterior to cleft between dorso-anterior loops, ridge extending from anterior of depression to center; parameres long, narrow, rounded spade-shape, emarginated ventro-basal edge; volsella with finger-like cuspis volsellaris and broad cusp-like digitus volsellaris, cuspis volsellaris with pointed end, flange extending on dorsal edge, digitus volsellaris with numerous small circular bumps, lobe on postero-dorsal edge, 2 teeth on medial ventro-basal corner of volsella, posterior tooth with lobe on posterior edge; penis valve of aedeagus with lateral arm of apodeme at anterior border, deep, wide, ventral concavity under ridge at base of apodeme, distal edge of valve wedge-shaped, proximal ventral edge of valve ending in tooth descending at roughly 45°, ventral edge with large laterally curved lip, serrated edge, serrations facing laterally on either side of aedeagus in dorsal view.

Type Material
Lenhart et al. (2013) - (worker) BRAZIL: Amazonas, Rio Negro [type not found]; Kempf, 1971: 372 (male)