Trachymyrmex jamaicencis (André)

Mayhé-Nunes, Antonio J. & Brandão, Roberto F., 2007, Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 3: The Jamaicensis group (Hymenoptera: Formicidae), Zootaxa 1444, pp. 1-21 : 13-15

Trachymyrmex jamaicencis (André)

( Figs. 19–22 , 29)

Atta (Acromyrmex) jamaicensis André, 1893:149 (worker). Wheeler, 1907: 712 (gyne and male). Weber, 1966: 588 (figures of gyne and worker head). Kempf, 1972: 253 (catalog). Bolton, 1995: 420 (catalog).

Atta (Trachymyrmex) sharpii Forel, 1893: 372 (worker). Wheeler, 1907: 712 (synonymy).

Atta (Trachymyrmex) maritima Wheeler, 1905: 107 (worker). Wheeler, 1907: 712 (synonymy).

Acromyrmex (Trachymyrmex) jamaicensis var. maritima: Mann, 1920: 428 (revived from synonymy). Kempf (1972: 253) catalog. Bolton (1995: 420) catalog NEW SYNONYMY.

Trachymyrmex jamaicensis var. frontalis Santschi, 1925 (worker) NEW SYNONYMY.

Trachymyrmex jamaicensis cubaensis Wheeler, 1937 (worker). NEW SYNONYMY.

[Types not examined]

Worker measurements (n = 10). TL 5.3 (4.5–5.7); DHL 1.42 (1.23–1.49); HW 1.38 (1.25–1.48); IFW 0.83 (0.69–0.94); ScL 1.17 (1.08–1.31); HWL 0.86 (0.78–0.92); MeL 2.03 (1.75–2.18); PL 0.42 (0.32–0.48); PPL 0.53 (0.45–0.58); GL 1.48 (1.23–1.58); HfL 2.04 (1.75–2.18).

Worker description: Dark ferruginous, with lighter spots on coxae and inferior margin of pronotum; in most specimens, the head and gaster are darker than the rest of the body. Integument opaque and finely granulose. Pilosity: scarce very short curved hairs confined to body projections, more abundant on antennal scapes and gaster tip.

Head, in full face view ( Fig. 19 ), from a little longer than broad to a little broader than long (DCI average 100; 92–117). Outer border of mandible feebly sinuous; eight teeth on chewing border, gradually diminishing in size towards base. Clypeus median apron without conspicuous projections. Frontal area shallowly impressed. Frontal lobe semicircular, moderately approximate to moderately expanded (FLI average 60; 50– 67), with faintly crenulated free border, lacking prominent denticles on the antero-lateral border. Frontal carina moderately diverging caudad, reaching the antennal scrobe posterior end in a small tooth at the posterior margin of head; preocular carina posteriorly ending in the posterior margin of head as a stout blunt spine larger than the frontal carinae projections. Occipital spine slender and as long as the preocular carinae projections. Supraocular projection tuberculiform. Paired denticulate vertexal carinae indicated by a series of weakly connected piligerous denticles, flanking the shallowly impressed sagital furrow, which in front joins the transverse impression of frons behind the frontal area. Inferior corner of occiput, in side view, with a small denticulate ridge. Eye convex, weakly surpassing the head lateral border, with 13 facets in a row across the greatest diameter. Antennal scape, when lodged in the scrobe, projecting beyond the tip of the preocular carinae projections by nearly one fourth of its length; gradually thickened towards apex, covered with small piligerous tubercles.

Mesosoma ( Figs. 20, 21 ). Pronotal dorsum marginate in front and on sides; antero-inferior corner with a strong and blunt tooth; inferior margin smooth; pair of median pronotal teeth absent or, when present, very small and arising from a common or separate bases, their tip microtuberculated or acute, not projected above the tip of the stronger lateral pronotal spines, which point obliquely upwards (with the pronotum in frontal view). Anterior pair of mesonotal spines nearly of the same length of the lateral pronotal pojections, with more robust base and upward directed; the second smaller, but much stronger than the almost always absent third pair. Anterior margin of katepisternum smooth, without a projecting tooth. Metanotal constriction impressed. Basal face of propodeum laterally marginated by a row of two denticles on each side; propodeal spines as long as the distance between their inner bases. Hind femora varying from a little shorter to a little longer than mesosoma length.

Waist and gaster ( Figs. 20, 22 ). Dorsum of petiolar node with one pair of truncate teeth, the sides parallel in dorsal view, with a series of lateral denticles; sternum without sagital keel. Postpetiole almost as long as broad in dorsal view, and shallowly impressed dorsally, with straight postero-dorsal border. Gaster, when seen from above, suboval. Tergum I with convex lateral faces separated from the dorsal face by a weak longitudinal row of piligerous tubercles on each side; anterior two thirds of dorsum with three glabrous shallow longitudinal furrows, separated by a pair of rows of piligerous tubercles. Sternum I without an anterior sagital keel.

Gyne and Male. See Wheeler (1907).

Material examined: BAHAMAS, Andros Island, Mangrove Cay, Mann col. 27 workers ( MZSP, USNM, CECL); ibidem, v–vi, 1904, W.M. Wheeler col. 4 workers ( MZSP); Fresh Creek, Mann col. 15 workers ( MZSP, USNM, CECL); Spanish Wells, Mann col. 6 workers ( USNM); Blutt, Mann col. 9 workers ( MZSP, USNM, CECL); South Bimini, 2.ix.1951, C. & P. Vaurie, 1 worker ( USNM). CUBA, Soledad, 12.vi.1927, W.S. Creighton, 6 workers ( MZSP); Nueva Gerona Island, 12.xi.1927, Creighton col. 6 workers ( MZSP, USNM). HAITI, Manneville, Mann col. 10 workers ( MZSP, USNM, CECL); Diquini, Mann col. 6 workers ( MZSP, USNM). JAMAICA, Kingston, M. Grabham (?), 3 workers ( USNM); St. Eliz., Malvern, 380m [18o 57´N, 77o 43´W], 12.iii.1984, J. Longino, specimen code JTLC 000006114, 2 workers ( JTLC). PUERTO RICO, Mona Island, 31.xi.1944, H.A. Beatty col., 4 workers ( MZSP, USNM). USA: Florida, Dania, (several dates in 1945), W.F. Buren, 35 workers ( MZSP, USNM, CECL); Marathon, 28.ii.1946, W.F. Buren, 9 workers ( MZSP, USNM); Big Pine Key, 10m, 16.ix.1982, P.S.Ward # 5745, “ground forager, hard wood, hammock”, specimen code JTLC 000006115, 2 workers ( JTLC).

Comments: The described infraspecies of T. jamaicensis are, in our view, local varieties based more on the degree of development of character states than in their presence or absence. Wheeler (1907) proposed the first two synonymies of T. jamaicensis ( T. sharpii Forel and T. maritima Wheeler ) at a time when he believed that this was a single species of the genus widely distributed in the West Indies. Some years later, however, Wheeler (1937) described other varieties of T. jamaicensis , and Mann (1922) revalidated T. jamaicensis var. maritima in a new concept. Although we were not able to study type material of all these varieties, in our comparative studies of the many available Antillean samples of T. jamaicensis , we were not able to discern samples that could merit specific recognition. Based on this and on the minor characters the authors used to differentiate infraspecies forms of T. jamaicensis , we are proposing the synonymies above.

Trachymyrmex jamaicensis presents noticeable variation in color and several morphological characters. In relation to the typical Jamaican form, specimens from Haiti, Cuba, and Florida are darker and present more slender and a little longer lateral pronotal spines. Specimens from the Bahamas may have, in relation to the other localities, very slender lateral pronotal spines, relatively short projections on the tip of frontal and preocular carinae, as well as smaller second mesonotal projection pair, thinner occipital projections, and longer petioles. Some specimens from Cuba and Puerto Rico also present relatively long petioles. Workers from Cuba and Florida may have two midpronotal teeth, and in the case of some Florida specimens, arising from separate bases. All Florida specimens present mesosomal projections stouter than in other samples and more expanded frontal lobes in relation to specimens from other localities, but agree in all other details with the description we provide above.

Wheeler (1905) described the nesting habits of T. jamaicensis (cited by him as Atta [T.] maritima ), that prefer to nest in pure foraminiferous sand of the seashore at or just above the high water mark, but may be found more inland as well. The inconspicuous nests are surmounted by very flat moundlets, with a single somewhat eccentric entrance, leading to one to many small ovoid chambers. The fungus is nourished with buds, small flowers, bits of dead and living leaves and caterpillar excrement. The workers feign death when disturbed. Weber (1967) visited Bimini Islands in 1959 to examine nests of this species and to secure fungus cultures. He only found nests in the northwestern portion of the South Island among scrub vegetation. He described the nest entrance crater, which may attain up to 50mm height and 3 to 8 chambers, which can extend to a depth of 70cm. Not all chambers were filled with fungus gardens, that when present were in the form of friable lamellae suspended from rootlets. The ants foraged at night or early mornings, ceasing when the sun shone on nests. The workers feigned death or quickly ran into the crater when disturbed. The largest workers in the colony were responsible for the foraging or for bringing up sand from the nest, while the smallest and palest stayed inside the nest and took care of the fungus garden, to which they brought yellowish flower stamens, woody particles, green dicot leaf sections and possibly insect feces. Weber (1972) depicted a cluster of inflated hyphal ends freshly removed from a garden of T. jamaicensis and presented a drawing of ends of two hyphae, showing stages in the development of inflations.

Atta (Trachymyrmex) sharpi Forel, 1893 was synonymyzed with Trachymyrmex jamaicensis by Wheeler in 1907. Notwithstanding, Kempf (1972) cited this name as valid in his catalog, and so Bolton (1995) considered Kempf´s move as a revalidation of the name T. sharpi . However, Kempf commented on all taxonomic novelties he proposed in the catalog, not citing any Trachymyrmex in this list. Also, the Museu de Zoologia da USP keeps the original cards Kempf used to construct the catalog, but the information regarding Wheeler´s synonymy is missing in the cards related to T. sharpi . We interpret the citation in the catalog as an error and are thus not proposing again the synonymy of T. sharpi , with which we fully agree. This is not the case of T. maritimus , which was revived from synonymy by Mann (1920), cited by Kempf (1972) as a subspecies of T. jamaicensis , and that we consider now a synonym of T. jamaicensis .

The first known fossil of any fungus-growing ant, Trachymyrmex primaevus , was described by Baroni Urbani (1980) from several Dominican amber pieces. He compared this species with T. jamaicensis , the only known valid species of the island of Hispaniola at the time of the description, although he stated that the definite relationships of the fossil to the known recent Trachymyrmex species were not clear. Baroni Urbani´s reconstruction of T. primaevus workers clearly shows heavily longitudinally striate mandibles and preocular carinae curved inwards, characters shared with Trachymyrmex of the Septentrionalis group, distributed today all over the Americas, but hitherto unknown in Caribbean localities. We will deal formally with the fossil species and the Septentrionalis species group in a forthcoming paper.

Figures

FIGURES 19 – 22. Scanning electron micrograph of Trachymyrmex jamaicensis, worker from USA: Florida, Marathon. 19. Head in frontal view. 20. Mesosoma and waist in lateral view. 21. Mesosoma, waist and gaster in dorsal view. 22. Waist and gaster in dorsal view. All scale bars = 250 μm.