Strumigenys nitens, Santschi 1932

Booher, Douglas B., Prebus, Matthew & Lubertazzi, David, 2019, A taxonomic revision of the Strumigenys nitens and simulans groups (Hymenoptera: Formicidae), two Caribbean radiations of leaf litter ants, Zootaxa 4656 (2), pp. 335-358 : 345-348

Strumigenys nitens, Santschi 1932

( Figs. 2b , 5 & 6 )

Strumigenys nitens Santschi 1932: 413 , fig. 2. Neotype worker (here designated): CUBA: Holguín: 2km N La Melba , 20 28 N, 74 49 W, 400 m, 22.viii.2001, P. S. Ward#14424-5, sifted litter (leaf mold, rotten wood), rainforest (CASENT0106246) [MCZC, secondary specimen code MCZ-ENT00681484]. Codiomyrmex nitens Santschi : Weber 1934: 52. First combination in Codiomyrmex . Dorisidris nitens Santschi : Brown 1948: 116. First combination in Dorisidris . Pyramica nitens Santschi : Bolton 1999: 1672. First combination in Pyramica . Strumigenys nitens Santschi : Baroni Urbani & de Andrade 2007: 125. Combination reinstated.

Non-type material examined. BAHAMAS: North Andros Island: north of Stafford Creek Bridge , 24.9052 - 77.9394, 11m, 14-Nov-1996, M. Deyrup & L. Davis, rocky roadside area, 1 worker (CASENT0799748) [ DBBC] . CUBA: Same data as neotype: 2 workers (bottom and middle point) and 1 dealate gyne (top point) on same pin (CASENT0914607) [ CASC]; 3 workers (MCZENT00594122) [ MCZC]. Pinar del Rio: 14km WSW Viñales 22 34 N, 83 50 W, 150 m, 30.viii.2001, P.S. Ward #14473-7, sifted litter (leaf mold, rotten wood), trop. moist forest, 1 worker (CASENT0758246) [ PSWC] .

Diagnosis. Strumigenys nitens can be distinguished from other congeners in the nitens group, except for S. hubbewatyorum , by the dental count of five + two intercalary denticles. This species is most closely related to S. hubbewatyorum but can be distinguished from it by lighter coloration ( S. nitens is orange to light yellowish brown and S. hubbewatyorum is dark brown), absence of elongate differentiated setae on vertices of their cephalic margin (two elongate filiform to subflagellate erect and differentiated setae present in S. hubbewatyorum ), short decumbent ground pilosity on mesosoma (shorter than eye width and simple in S. nitens and longer than eye width and wavy ground pilosity in S. hubbewatyorum ), smaller size, and shorter femur (WL = 0.51–0.56 HL = 0.47–0.50 FL = 0.27– 0.36 vs. S. hubbewatyorum WL = 0.57–0.62, HL = 0.52–0.53, FL = 0.39–0.42). This species is also closely related to S. caiman , but can be distinguished from it by the following additional characters: inner mandibular margin with three teeth; apex of mandibles with two teeth and two intercalary denticles vertically arranged: the uppermost is spiniform, followed by two small intercalary denticles that appear to arise from the margin of the lowermost tooth, which is elongate-triangular (see Fig. 2b ); mandibles shorter (MI 31–33 vs. 38–39 in S. caiman ); antennal scape is longer (SI 61–74 vs. 56–60); mesosoma slightly more elongate (WL 2.3 times PW vs. 2.1–2.2); eye larger, diameter greater than the maximum width of the antennal scape. The following characters separate S. nitens from S. zemi and S. convexiceps : mandibles relatively long (MI 24–29 in S. zemi and S. convexiceps ) petiolar node narrow in dorsal view, about half the width of the postpetiole; mesosoma relatively elongate (WL 1.7–1.8 times PW in S. zemi and S. convexiceps ).

Neotype worker measurements. HL = 0.47; HW = 0.36; ML = 0.16; PW = 0.23; SL = 0.23; FL 0.33; HT = 0.30; EL = 0.06; TL = 2.02; WL = 0.52; CI = 77; MI = 33; SI = 62

Non-type worker measurements (n=6). HL = 0.43–0.50 (0.48); HW = 0.32–0.38 (0.36); ML = 0.13–0.16 (0.15); PW = 0.22–0.25 (0.23); SL = 0.19–0.24 (0.22); FL = 0.27–0.36 (0.34); HT = 0.28–0.32 (0.3); EL = 0.06–0.07 (0.07); TL = 1.84–2.19 (2.06); WL = 0.44–0.56 (0.53); CI = 74–78 (75); MI = 30–33 (32); SI = 59–68 (61)

Worker description. Mandibles in full face view and at full closure elongate-triangular, strongly tapering apically, and longer than the apical antennal segment in full face view; MI 30–33. Distalmost third tooth of the inner mandibular margin and extreme apices of mandibles engage, and a broad subovate gap is present between them through which the broad labral lobes are visible. Inner mandibular margin with two conical teeth whose apices are widely separated in addition to a third elongate-triangular tooth whose apices touch at full closure; the first about one-quarter of the margin length from the base, the second about one-half way along the margin, and the third at three-quarters the way along the margin. Apex of mandibles two teeth arranged vertically, with the upper long and spiniform and the lower elongate-triangular; two intercalary denticles arise between these apical teeth along the margin of the apicoventral tooth (see Fig. 2b ). Clypeus and upper scrobe margins have fine faint longitudinal striolate-punctate sculpture, traces of which are also present on the cephalic dorsum between the frontal carinae. Antennal scapes long: SI 58–68. Lateral margins of the head roughly parallel and the posterior margin shallowly concave in full-face view. Dorsum of head with elongate, spatulate setae which curve toward the midline. Scrobal margin with a single pair of short slightly expanded setae at apicoscrobal position. Compound eye large: diameter greater than to the maximum width of the antennal scape. In profile view, faint punctate sculpture present between the compound eye and the postbuccal impression.

Mesosoma elongate: WL 2.3 times PW. Uniformly smooth and shining, with faint traces of sculpture around the propodeal spiracle and lamellae. Dorsal surface with elongate, spatulate setae which curve toward the midline.

Petiolar node narrow, roughly 1/2 as broad as postpetiole in dorsal view. Petiolar peduncle covered in light punctate sculpture, but dorsal surface of petiole and postpetiole smooth and shining. Dorsal surfaces of petiole and postpetiole with elongate, spatulate setae.

Basigastral costulae present only on the limbus and the extreme base of the first gastral tergite, the remainder of which is smooth and shining. First gastral tergite with numerous long, fine, tapering setae.

Head, mesosoma, gaster, and appendages uniformly light reddish or yellowish brown.

Distribution and Ecology. The lost type of S. nitens was collected from Sierra del Rosario, located in present-day Artemisia province, which reaches an elevation of 450 meters. Other specimens have been collected in Pinar del Rio province in Valle Viñales National Park from lowland tropical moist forest, and from lowland tropical rainforest in Holguín province. In both of the latter localities, specimens were collected from leaf litter extracted via the Winkler method. The single specimen collected on North Andros Island is also from a low elevation habitat and generally matches S. nitens as described here. It does differ slightly in having a pair of elongate pronotal setae and is smaller than any of the other S. nitens we examined. However, without additional material to determine the stability of size and pilosity characters that differ slightly from the Cuban S. nitens material, we conservatively identify this specimen as a worker of S. nitens .

Taxonomic notes. The type of S. nitens is missing from its mount at NHMB, so we rely on Santschi’s original description of the species as a guide to designate a neotype. Bolton (2000) redescribed S. nitens from specimens collected during later expeditions ( S. caiman in the present study), but his description was at odds with the original description ( Santschi 1932), specifically with respect to dental count. Santschi noted that the total dental count was five, with two short teeth along the inner margin of the mandible and three teeth apically (the upper two long, and the lower one shorter). An illustration of the mandibles in full face view and oblique antero-dorsal view accompanied the description (reproduced in Fig. 2a ). It appears that the third tooth from the base, or uppermost apical tooth, is shifted toward the base, away from the mandibular apex. This matches the specimens that we describe as S. nitens , but not those of S. caiman , where the third tooth from the base is shifted forward, in line with the three other apical teeth when in full-face view (see Fig. 2c ). Additionally, in S. nitens , the diastema between the lower teeth at the mandibular apex is interrupted by two minute intercalary denticles (see Fig. 2b ), which may have been overlooked by Santschi (1932).

Figures

FIGURE 2. Comparison of full-face view and mandibles in oblique antero-dorsal view of: a) reproduction of original Santschi (1932) illustration of Strumigenys nitens b) Strumigenys nitens (CASENT0914607) c) Strumigenys caiman (MCZ- ENT00644270).

FIGURE 5. Worker of Strumigenys nitens (CASENT0914607; photographer Zach Lieberman): a) dorsal view b) profile view c) full-face view. Scale bars 0.2 mm.

FIGURE 6. Dealate queen of Strumigenys nitens (CASENT0914607): a) dorsal view b) profile view c) full-face view. Scale bars 0.2 mm.