Sericomyrmex saussurei Emery, 1894

Jesovnik, Ana & Schultz, Ted R., 2017, Revision of the fungus-farming ant genus Sericomyrmex Mayr (Hymenoptera, Formicidae, Myrmicinae), ZooKeys 670, pp. 1-109 : 82-91

Sericomyrmex saussurei Emery, 1894 Figures 56, 57(Worker); Figure 58(Queen and male); Figure 59(Larva); Figures 21, 60 (Map)

Sericomyrmex saussurei Emery, 1894: 223. Holotype worker: BRAZIL, Mato Grosso, [-13, -56], ANTC25804, 1886, P. Germain (MSNG: 1w, USNM00445513).

Sericomyrmex burchelli = Forel, 1905: 183. syn. n. Type material examined: BRAZIL, Goiás [-15.9, -50.3], W. J. Burchell (MHNG: 1q, USNM00445563; 1m, USNM00445564).

Sericomyrmex impexus = Wheeler, 1925a: 54. syn. n. Type material examined: GUYANA, Cuyuni-Mazaruni, Kartabo [6.3551, -58.6944], Jul-Aug 1920, W. M. M. Wheeler (MCZ: 2w, MCZ-ENT00021138).

S. urichi maracas = Weber, 1937: 395. syn. n. Type material examined: TRINIDAD AND TOBAGO, San Juan-Laventille, Maracas Valley [10.75, -61.43], 1 Oct 1935, N. A. Weber, NAW373-1 (MCZ: 2w, MCZ23048).

S. saussurei worker diagnosis.

Medium-sized species; mandible usually dorsally striate, frontal carina complete; frontal lobe triangular; eye convex, moderately protruding from sides of head, covered with thick white layer; posterior cephalic emargination abruptly to gradually impressed, mesosomal tubercles from low and obtuse to well developed; first gastral tergite with lateral carinae well developed, dorsal carinae weak to well developed.

S. saussurei worker description.

Measurements in mm, range (holotype): HWe 0.88-1.23 (0.98) HW 0.88-1.23 (NA) HW1 0.82-1.32 (1) HW2 0.92-1.56 (1.13) HW3 0.55-0.84 (0.7) IFW1 0.59-0.88 (0.67) IFW2 0.19-0.36 (0.24) HL1 0.84- 1.15 (0.96) HL2 0.76-1.08 (0.87) SL 0.62-0.86 (0.73) EL 0.12-0.24 (0.14) Om 7-11 (NA) WL 1.1-1.64 (1.35) PL 0.21-0.38 (0.25) PPL 0.15-0.3 (0.2) GL 0.70-1.13 (1.13) HFL 0.75-1.38 (1.13) PW 0.61-0.85 (0.76) CI 94-112 (102) FLI 63-74 (69) SI 65-81 (74) OI 12-23 (15) CEI 4-14 (9) [N=68]

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

Head. In full-face view slightly broader than long (CI=104 ± 3), posterior corner rounded to angular, posterior cephalic emargination distinct (CEI=9 ± 2), gradually (Figure 7j) to abruptly (Figure 7k) impressed. Vertexal impression and frontal tumuli distinct. Mandible with 7-8 teeth, dorsally glossy and striate, sometimes striation reduced or absent (Figure 56b). Eye medium-sized (OI =15 ± 1), conspicuously convex, protruding slightly from side of head in full-face view, 7-9 ommatidia across largest diameter, always covered with thick, white layer (Figure 6 n–o), which makes discerning individual ommatidia difficult. Frontal lobe relatively wide (FLI=69 ± 2), triangular, slightly laterally expanded, with posterior margin shorter than medial. Frontal carina complete, reaching posterior cephalic corner. Antennal scape relatively short (SI=71 ± 2), not reaching posterior cephalic corner.

Mesosoma. Mesosomal tubercles from low and obtuse to moderately pronounced. Propodeal carinae low, reduced, sometimes with posterodorsal denticle.

Metasoma. Petiole and postpetiole with two low, short, serrate, longitudinal carinae dorsally, in 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 weak to well developed.

S. saussurei queen description.

Measurements in mm, range: HWe 1.3-1.38 HW 1.27-1.4 HW1 1.4-1.46 HW2 1.49-1.56 HW3 0.9-0.93 IFW1 0.95-1 IFW2 0.35-0.4 HL1 1.27-1.33 HL2 1.18-1.25 SL 0.9-0.96 EL 0.23-0.29 Om 20-24 EW 0.08-0.1 WL 2-2.16 PL 0.43-0.56 PPL 0.25-0.3 GL 1.83-1.95 HFL 1.22-1.6 PW 1.15-1.2 FWg 7.04-7.37 HWg 4.73-4.73 CI 98-106 FLI 70-75 SI 65-72 OI 17-21 [N=6].

Head. Mandible with 8-9 teeth, dorsally glossy and smooth, finely transversely striate only along masticatory margin. Preocular carina fading posterior to eyes. Eye large (OI=19 ± 2), convex, partially covered with white layer, layer thinner than in workers, 20-24 ommatidia across largest diameter. Frontal lobe as in worker, antennal scape not reaching posterior cephalic corner.

Mesosoma. Scutum in dorsal view notauli faint, median mesoscutal line visible only anteriorly. Parapsidal lines thin, slightly curved. Groove separating axillae in dorsal view weakly transversely costate. Scutellum in dorsal view narrowing posteriorly, posterior margin medially with wide, shallow V-shaped notch. Propodeal carinae low, posteriorly diverging, with posterodorsal denticles.

Metasoma. First gastral tergite with lateral carinae strongly developed, dorsal carinae weak, anteromedian groove visible.

S. saussurei male description.

Measurements in mm, range: HWe 0.74-0.9 HW 0.62-0.7 IFW1 0.3-0.32 IFW2 0.16-0.19 HL1 0.66-0.68 SL 0.65-0.74 EL 0.25-0.3 Om 23-26 EW 0.13-0.14 WL 1.6-1.72 PL 0.28-0.38 PPL 0.18-0.22 GL 1.18-1.4 HFL 1.52-1.78 PW 0.74-0.88 IOD 0.56-0.61 FWg 4.73-5.23 HWg 3.15-3.4 CI 112-133 FLI 34-41 SI 79-91 OI 32-36 [N=6]

Head longer than broad (CI=125 ± 7), eye large (OI=34 ± 1) and convex, 23-26 ommatidia across the largest diameter. Preocular carina long, extending posteriorly almost to lateral ocellus, slightly curved medially before fading. Notauli and mesoscutal line well developed, integument surrounding parapsidal lines sometimes darker colored, groove between axillae sometimes with one short costa. Propodeum smooth, without protuberances except small spiracular tubercle. Petiole with lateral and dorsal serrate carinae, postpetiole with reduced lateral denticles.

S. saussurei larva.

Around eight setae on each side of lateral and dorsal body surfaces (i.e., ~16 total). Supra-antennal setae absent. Four genal setae on each side. Mandibular apical tooth divided. Labial denticles present anterior to sericteries. First thoracic segment without multidentate spinules. Numbers of ventral setae: two on T1, two on T2, three on T3, and around 10 on abdomen (not including anal setae). Single pair of setae anterior to anal opening.

S. saussurei geographic range.

Bolivia, Brazil, Ecuador, French Guiana, Guyana, Peru, Suriname, Trinidad and Tobago, Venezuela. Map: Figure 21, Figure 60.

S. saussurei notes.

The species most similar to S. saussurei is its sister species S. amabilis , but amabilis can easily be distinguished by its more or less flat eyes lacking the white layer, and usually by geography (Figure 21). S. mayri , which, like S. saussurei has striate mandibles, is larger, has a wider head, and flat eyes without a white layer. The smaller species S. parvulus and S. opacus may have a similar white layer over the eyes, but their eyes are small and flat, and the white layer is thinner than in saussurei , sometimes incomplete and with individual ommatidia still distinguishable (Figure 6 l–m). Also, both parvulus and opacus have smooth mandibles. The white layer is not as distinct in the queen of S. saussurei , but the combination of body size, pilosity, and frontal lobe shape are enough to separate the S. saussurei queen from those of the sympatric mayri , bondari , and parvulus .

Several populations of S. saussurei have faintly striate or completely smooth mandibles. The atypical smooth-mandibled state was in at least one case consistent within an entire nest; all individuals in a colony collected in Viçosa (Brazil) have smooth mandibles. Individuals with intermediate states are sometimes encountered, with mandibles faintly or partly striate. Smooth-mandibled saussurei are distributed more or less across the entire range of the species, but are more concentrated in eastern Brazil (Figure 60). However, in the molecular phylogeny the two forms cluster into two imperfect subclades in which some striate-mandibled forms mix with predominantly smooth-mandibled forms and vice versa, and a similar pattern is observed in principal component analyses of the morphological measurement data (Figure 5h). More data are clearly needed to determine if the smooth-mandibled variant represents a separate species. Here we choose to include both forms in a single species because they are morphologically very similar, the molecular evidence is indecisive, and this character is generally plastic (e.g., both amabilis and mayri , which typically have striate mandibles, likewise have a few populations with smooth or smoother mandibles).

Interestingly, the white layer on the eyes of saussurei is exceptionally consistent compared to character-state distributions in other Sericomyrmex species. In fact, it is among the most consistent of all morphological characters across all Sericomyrmex species. In all specimens of S. saussurei examined, from across a large geographic range (Figure 21), the eyes are convex and covered with a thick white layer. Similar white layers are also seen in parvulus and opacus . In those species, however, the layer itself is thinner and often incomplete, and the eyes are generally smaller and flat, creating a distinctly different appearance (Figure 6 l–m). Also, in both parvulus and opacus the layer is completely absent in some individuals or populations. In the remaining species of Sericomyrmex the eyes are uncoated, without a white layer. It would be interesting to determine the biological significance of this layer and to analyze its chemical properties. Based on our SEM images it seems to be an extension of the waxy, crystal-like cuticular layer found on the integuments of workers and queens in all Sericomyrmex species (Figure 6 b–c), but which is absent in males and in callow workers (Figure 6 d–f), as well as in some individuals of S. maravalhas . Why this layer extends to and completely covers the eyes in some species but not others remains unknown.

Synonymies. No character states in S. impexus and S. urichi maracas distinguish them from S. saussurei . The two examined syntypes of impexus are only slightly larger in size than the single saussurei type specimen, but well within the size range for the species. When describing impexus Wheeler (1925a) only distinguishes it from urichi and lutzi . Likewise, in his description of urichi maracas Weber (1937) simply lists differences from urichi , to which this species is not very closely related ( S. urichi is a junior synonym of S. mayri ). S. burchelli , described only from a queen and a male, can be recognized as belonging to saussurei based on morphological measurements, and in the queen also by a thin white layer partially covering the eye. Forel (1905) separates the queen of burchelli from saussurei by its sparser hair, more developed petiole and postpetiole, and less developed metanotal tubercles. However, this comparison must have been made to a saussurei worker, because the queen of S. saussurei was unknown prior to the present study. Consequently, Forel’s (1905) differences are due both to differences between the worker and queen castes as well as to observed within-species variation.

Material examined.

BOLIVIA: Santa Cruz: 10 km NW Terevinto, -17.6667, -63.45, 380m, 9 Dec 1993, P. S. Ward; Aserradero Moira, -14.5667, -61.2, 180m, 27 Nov 1993, P. S. Ward; BRAZIL: Amazonas: Floresta de Tapauá, km 4, -6.01, -63.1, 69m, 13 Oct 2013, I. O. Fernandes; Manaus, Br 174, Km.70, [-2.26, -60.04], 95m, 30 Aug 1995, H. Vasconcelos; Pres. Figueredo, I. Pe Inchado, [-2.02, -60.02], 26 Aug 1994, Queiroz; Bahia: CEPLAC, arboreto, -14.7535, -39.2313, 11 Oct 2013, J. H. C. Delabie; Ilhéus, Ponta do Ramo, Cacau 02, -14.5294, -39.0619, 28 Aug 1998, J. R. Maia; Itabuna, Ferradas A27, -14.8258, -39.4044, 21 Sep 2000, J. R. M. Santos; Itororó, -14.9744, -40.0502, 11 Aug 2000, J. R. M. Santos; Maraú, Fazenda Água Boa, -14.5847, -39.2672, 1 Jul 1997, J. R. M. Santos; Salvador, [-12.9833, -38.5167], 1 Oct 2012, T. S. Melo; Uruçuca, -14.5847, -39.2672, 16 Dec 1997, J. R. M. Santos; Goiás: Cavalcante, Serra da Contenda, -13.4951, -47.5504, 15 Oct 2004, R. R. Silva, B. H. Dietz; Niquelândia, -14.0166, -48.3, 24 Sep 1995, R. Silvestre, B. H. Dietz, C. R. F. Brandão; Maranhão: Bom Jardim, REBIO Gurupi Parcela 01 A2, -3.9258, -46.7712, 19 Sep 2014, A. Y. Harada; Estreito, Fazenda Itaueiras, -6.5317, -47.3711, 1 Jun 2005, R. R. Silva, R. M. Feitosa; Estreito, João Lisboa, -6.5317, -47.3711, 1 Jun 2005, R. R. Silva, R. M. Feitosa; Minas Gerais: Camacan, Serra Bonita, -15.3907, -39.5634 ± 6m, 789m, 20 Mar 2009, J. Sosa-Calvo; Serra de Ricardo Franco State Park, -14.9076, -60.0646, 200m, 7 Feb 2014, J. Maravalhas; Viçosa, Mata do Seu Nico, -20.7833, -42.8333, 8 May 2013, R. Jesus, J. Chaul; Viçosa, UFV Mata da Biologia, -20.7578, -42.8636, 10 Oct 2015, J. Chaul, S. Epifânio; Pará: Alter do Chão, -2.4607, -54.926 ± 6m, 39m, 27 Jan 2009, J. Sosa-Calvo; Goianésia, Faz. Rio Capim, [-3.8384, -49.0986], 16 Jun 2003, A. M. Elizabeth; Gurupá, [-1.197, -51.7], 18 Oct 2003, J. M. S. Vilhena; Marituba, Cacau, [-1.3666, -48.3333], 16 Oct 2004, J. R. M. Santos; Melgaço, Caxiuanã, ECFPn IV Transecto 9-100) Winkler #5, -1.7248, -51.4230, 27 Jun 2003, A. Y. Harada; Paranapuebas Palmares, Lote BPR Mensa Ponto: 35583, -5.8072, -49.8325, 9 Apr 2008, M. Martíns; Tailândia, Faz. Marupiara, Parcela 05, -2.8121, -48.5122, 25 Apr 2013, M. Tavares, A. Palmeira; Rio de Janeiro: Nova Iguaçu, ReBio Tinguá, -22.5705, -43.4141, 2 Feb 2002, A. Mayhe, S. Veiga-Ferreira; Restinga da Marambaia, [-23.0685, -43.9531], P. S. Meneguete; Teresopólis, PN Serra dos Órgãos, -6.5317, -47.3711, 23 Nov 1999, Racha, B. H. Dietz, Rosa; Rondônia: Jaci-Paraná, km 0, subparcela 100, -9.2656, -64.2125, 94m, 27 Jan 2013, I. O. Fernandes; Ji- Paraná, -10.7997, -61.5947, 273m, 7 Oct 2008, T. R. Schultz; São Paulo: Cananéia, Ilha do Cardoso, -28.0968, -47.9298, 24 Dec 2002, R. R. Silva, C. R. F. Brandão, C. Scott; Jacupiranga, [-24.7055, -48.0167], 1 Nov 1963, F. Plaumann, C. Kempf; Jureia-Itantins, -24.54416, -47.235; Picinguaba, P.E. Serra do Mar, -23.3361, -44.8375, 1 Apr 2001, C. R. F. Brandão; Tocantins: Aguiarnopólis, -6.6137, -47.4814, 14 Jan 2005, R. R. Silva, R. Silvestre; Araguacema, Rio Tiririca, -8.9886, -49.6675, 16 Nov 2005, R. R. Silva, R. M. Feitosa; Babaçulândia, -7.0878, -47.8286, 10 Dec 2001, R. R. Silva, N. L. Albuquerque; Goiatins, -7.9413, -47.1586, 3 May 2005, R. R. Silva, B. H. Dietz; Paraná, -12.9343, -47.9618, 13 Oct 2004, R. R. Silva, B. H. Dietz; Recursolândia, -8.7579, -47.0388, 9 May 2005, R. R. Silva, B. H. Dietz; COLOMBIA: Amazonas: Leticia, Reserva Forestal Del Río Calderón, Estac. Biol. El Zafire, -4.0058, -69.9125, 146m, 1 Dec 2007, L.E. Franco, S. Florez; PNN Amacayacu Matamata, -3.6833, -70.25, 150m, 15 Oct 2000, A. Parente; Putumayo: PNN La Paya Cabaña Viviano Cocha, -0.1166, -74.9666, 350m, 1 Jun 2003, R. Cobete; ECUADOR: Orellana: Tiputini Biodiversity Station, -0.6333, -76.1333, 220m, 14 Feb 2002, K. T. Ryder Wilkie; FRENCH GUIANA: Cayenne: Kourou, 5.096, -52.404, 18 Dec 2014, M. Fichaux, Orivel; GUYANA: Potaro-Siparuni: Iwokrama, Kurapakari base camp, [4.6698, -58.6854], 60m, 9 Apr 1996, T. R. Schultz, U. G. Mueller; Upper Takutu-Upper Essequibo: Acari Mountains, nr. Romeo’s camp, 1.3833, -58.9333, 282m, 10 Oct 2006, J. Sosa-Calvo; PERU: Cajamarca: Cajamarca, 32 km W Jaen, -7.1667, -78.5167, 600m, 19 Jan 1955, E. I. Schlinger, E. S. Ross; Madre de Dios: PN Pampas de Heath, Río Heath, -12.8333, -68.8333, 26 Jul 1991, B. L. Fisher; Puerto Maldonado, Los Amigos Biol. Station, trail 3, Huangana, -12.569, -70.1008, 277m, 9 Oct 2004, T. R. Schultz, J. Sosa-Calvo; Tambopata Reserve, -12.8187, -69.3636, 224m, 1 Aug 2012, A. Ješovnik; SURINAME: Sipaliwini: Lely Mountains, 4.4507, -55.2302, 550 m, 29 Oct 2005, J. Sosa-Calvo, R. Badal; Nassau Mountains, 4.8172, -54.6067, 514m, 3 Nov 2005, J. Sosa-Calvo; VENEZUELA: Bolívar: Río Tawadu, Nichare Field St., 6.4333, -64.8833, 200m, 9 Feb 1966, D. M. Olson.