Sericomyrmex mayri

Workers mostly forage alone but will sometimes form short, dense foraging columns in the immediate area of the nest entrance.

Identification
Jesovnik and Schultz (2017) - Large species; head broad; frontal lobe narrow, directed anterad; mandible usually striate; frontal carina often reduced, incomplete; eye flat to mildly convex; posterior cephalic margin shallow, abruptly to gradually impressed; posterior cephalic corner usually angled; mesosomal tubercles low and obtuse, first gastral tergite with lateral carina well developed, dorsal carinae absent or faint.

S. mayri can be separated from both Sericomyrmex amabilis and Sericomyrmex saussurei by its large size, broad head, narrow frontal lobes, and gaster lacking anteromedian dorsal carinae. In addition, saussurei has eyes covered with a thick white layer, which is never the case in mayri. Sericomyrmex lutzi is similar in size, but lutzi has a characteristic, much deeper cephalic emargination and smooth mandibles. In addition to worker characters, the S. mayri queen can be separated from the sympatric S. saussurei queen by its more pronounced petiolar denticles.

Variation within S. mayri includes the scape length, the head shape, and mandibular striation. As with Sericomyrmex amabilis and saussurei, two other species with striate mandibles, some individuals or populations of S. mayri have smooth or faintly striate mandibles. These alternative states are encountered less commonly in mayri than in the other two species, mostly in populations from Trinidad and Tobago. Intermediate-state workers (i.e., those with faint mandibular striation) were collected at the same locality and, indeed, were found within the same nest as workers with typically striate mandibles. A callow worker of mayri studied with SEM had smoother, faintly striate mandibles), so some observations of smooth mandibles may be due to sampling of recently eclosed workers, but this is unlikely to explain smooth-mandibled foragers.

The presence/absence of the anteromedian dorsal gastral carinae and robustness of the lateral gastral carinae are also variable in mayri. Typically, both carinae are present, but in some specimens the anteromedian carinae are very faint or absent, while lateral carinae can be weak to robust. The posterior cephalic emargination can be very shallow, so that the posterior margin of the head appears almost straight (e.g., specimens from Minas Gerais, Uberlandia, Brazil, and the type series of Sericomyrmex moreirai). The shape of the head varies to some extent, from distinctly broad in some specimens to more narrow in others (the CI range is wide: 101–115).

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, Colombia, Cuba, Ecuador, French Guiana, Guadeloupe, Guyana , Peru, Suriname, Trinidad and Tobago , Venezuela.

Nomenclature

 *  mayri. Sericomyrmex mayri Forel, 1912e: 194 (w.) BRAZIL.
 * Status as species: Wheeler, W.M. 1916c: 10 (in key); Emery, 1924d: 339; Borgmeier, 1927c: 127; Kempf, 1972a: 229; Bolton, 1995b: 382; Ješovnik & Schultz, 2017a: 61 (redescription).
 * Senior synonym of arawakensis, harekulli, luederwaldti, moreirai, urichi: Ješovnik & Schultz, 2017a: 61.
 * Senior synonym of muelleri: Ješovnik & Schultz, 2017b: 202.
 * muelleri. Sericomyrmex opacus var. muelleri Forel, 1912e: 195 (q.) BRAZIL.
 * Subspecies of opacus: Emery, 1924d: 339; Borgmeier, 1927c: 128; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of mayri: Ješovnik & Schultz, 2017b: 202.
 * urichi. Sericomyrmex urichi Forel, 1912e: 193 (w.) TRINIDAD.
 * Status as species: Wheeler, W.M. 1916c: 11 (in key); Wheeler, W.M. 1922c: 13; Emery, 1924d: 339; Weber, 1937: 395; Weber, 1945: 40; Kempf, 1972a: 230; Bolton, 1995b: 382.
 * Junior synonym of mayri: Ješovnik & Schultz, 2017a: 61.
 * luederwaldti. Sericomyrmex luederwaldti Santschi, 1925b: 15 (w.) BRAZIL.
 * Status as species: Borgmeier, 1927c: 127; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of mayri: Ješovnik & Schultz, 2017a: 61.
 * moreirai. Sericomyrmex moreirai Santschi, 1925b: 16 (w.q.m.) BRAZIL.
 * Status as species: Borgmeier, 1927c: 128; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of mayri: Ješovnik & Schultz, 2017a: 62.
 * harekulli. Sericomyrmex harekulli Weber, 1937: 398, fig. 10 (w.) GUYANA.
 * Status as species: Weber, 1946b: 140; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of mayri: Ješovnik & Schultz, 2017a: 62.
 * arawakensis. Sericomyrmex harekulli subsp. arawakensis Weber, 1937: 399, fig. 11 (w.q.) GUYANA.
 * Subspecies of harekulli: Weber, 1946b: 141; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of mayri: Ješovnik & Schultz, 2017a: 62.

Jesovnik and Schultz 2017:

Worker
(lectotype): HWe 1.05–1.60 (1.4) HW 1.05–1.64 (1.43) HW1 1.02–1.68 (1.44) HW2 1.12–1.8 (1.6) HW3 0.74–1.12 (1.05) IFW1 0.66–1.00 (0.93) IFW2 0.24–0.40 (0.35) HL1 1.02– 1.52 (1.33) HL2 0.93–1.36 (1.21) SL 0.74–1.08 (0.99) EL 0.15–0.35 Om 10–13 WL 1.27–2.2 (1.84) PL 0.24–0.47 (0.4) PPL 0.18–0.35 (0.32) GL 0.92–1.42 (1.24) HFL 1.15–1.7 (1.58) PW 0.68–1.2 (1.05) CI 101–115 (105) FLI 59–68 (66) SI 61–76 (71) OI 11–26 CEI 5–19 (9) [N=103]

Pilosity. Pubescence dense, often lighter colored than integument, appressed to decumbent. Hairs straight to curved, darker in color at base, yellow to gray, appressed to suberect, mostly decumbent.

Head. In full-face view broader than long (CI=108 ± 3), posterior corner angular to acute, lateral margin of head straight, sometimes slightly convex. Posterior cephalic emargination distinct, shallow, usually abruptly, sometimes gradually impressed, variable within species and within colonies. Vertexal impression relatively deep, pronounced, sometimes extending anterad to include frons, frontal tumuli often distinct. Mandibles with 7–8 teeth, dorsally glossy, usually striate. Frontal carina straight to slightly curved laterally, usually fading before reaching posterior cephalic corner, sometimes complete. Eye small to medium-sized (OI=14 ± 1), flat to slightly convex, lacking white layer, 10–13 ommatidia across largest diameter. Frontal lobe triangular, narrow (FLI=63 ± 2), posterior margin much shorter than medial, lateral margin long, directed anterad. Antennal scape short (SI=68 ± 3), never reaching posterior cephalic corner.

Mesosoma. Mesosomal tubercles low and obtuse. Propodeal carinae low, without posterodorsal denticles, or denticles low and weak.

Metasoma. Petiole and postpetiole each with two low, short, serrate, longitudinal carinae dorsally, on petiole sometimes reduced to low denticles, best seen in dorsolateral view. Postpetiole usually with another pair of low carinae laterally. First gastral tergite with lateral carinae well developed, dorsal carinae absent or faint.

Queen
HWe 1.44–1.64 HW 1.48– 1.68 HW1 0.52–1.76 HW2 1.64–1.84 HW3 1.03–1.2 IFW1 0.98–1.13 IFW2 0.36–0.45 HL1 1.4–1.56 HL2 1.24–1.4 SL 0.96–1.09 EL 0.24–0.3 Om 16–21 EW 0.08–0.13 WL 2.12–2.5 PL 0.45–0.65 PPL 0.25–0.4 GL 1.76–2.21 HFL 1.5–1.85 PW 1.24–1.46 FWg 6.56–8.03 HWg 4.29–5.28 CI 100–109 FLI 64–72 SI 62–70 OI 16–19 [N=15]

Head. Mandible with 8–9 teeth, dorsally striate. Preocular carina fading posterior to eye, rarely (in one queen from Ecuador) 1–3 supraocular carinae also present, not reaching posterior cephalic corner. Eye large (OI=18 ± 1), convex, sometimes mildly notched posteriorly, 16–21 ommatidia across largest diameter. Frontal lobe as in worker, antennal scape not reaching posterior cephalic corner.

Mesosoma. Lateral pronotal tubercles low and obtuse. Scutum in dorsal view with notauli faint, median mesoscutal line sometimes anteriorly developed into weak costa, posteriorly with shallow longitudinal impressions on each side. Parapsidal lines thin, slightly curved. In dorsal view scutellum short, narrowing posteriorly, posterior notch shallow, sometimes continuing into median impression that divides scutellum in two lateral parts. Propodeal denticles reduced, low.

Metasoma. Petiole in frontodorsal view with two pointed, distinct dorsal denticles, and two smaller, lateral denticles. Postpetiole with two dorsal and two lateral short, low carinae, sometimes reduced to small denticles. First gastral tergite with lateral carinae strongly developed, dorsal carinae weak, anteromedian groove distinct.

Male
Measurements in mm, range: HWe 0.84–1.02 HW 0.71–0.84 IFW1 0.32–0.38 IFW2 0.15–0.27 HL1 0.72–0.8 SL 0.77–0.85 EL 0.31– 0.36 Om 24–32 EW 0.13–0.16 WL 1.88–2.05 PL 0.35–0.56 PPL 0.24–0.33 GL 1.32–1.8 HFL 1.9–2.2 PW 0.87–1.12 IOD 0.65–0.74 FWg 5.4–6.25 HWg 3.79– 4.29 CI 105–131 FLI 34–42 SI 78–96 OI 31–42 (N=8)

Head in full-face view longer than broad (CI=124 ± 8). Eye large (OI=36 ± 3), convex, 24–32 ommatidia across largest diameter. Preocular carina long, extended posteriorly beyond lateral ocellus, slightly curved medially before fading. Notauli and mesoscutal line well developed, surrounding integument usually lighter colored, often reticulate, groove between axillae with 1–4 transverse keels. Propodeum smooth, without any protuberances except spiracular tubercles. Petiole with two lateral and two dorsal low, serrate carinae, postpetiole with reduced lateral denticles.

Larva
Two to four setae on each side of lateral body surfaces, none dorsally. Supra-antennal setae present. Six genal setae on each side. Mandibular apical tooth divided. Labial denticles absent. First thoracic segment ventrally with multiple multidentate spinules, arranged in transverse rows. Numbers of ventral hairs: ten to fourteen on T1, six on T2, four to six on T3, two to eight on abdomen (not including anal setae). Single pair of setae anterior to anal opening, no additional setae laterally.

Type Material
Lectotype worker (here designated): Brazil, Rio de Janeiro, Niterói, [-22.8751, -43.2775], ANTC31816, A. Forel, (: 1w, CASENT0909370). Paralectotypes: same data as lectotype (MHNG: 1w, USNMENT00445567; 3m, USNMENT00445580).