Sericomyrmex saussurei

A well collected species with a broad distribution across northern South America. Collections of this species have been from forested areas and cerrado. The biology of Sericomyrmex saussurei has not been studied, general details about the biology of the genus are given here.

Identification
Ješovnik & Schultz (2017) - 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.

The species most similar to S. saussurei is its sister species Sericomyrmex amabilis, but amabilis can easily be distinguished by its more or less flat eyes lacking the white layer, and usually by geography. Sericomyrmex mayri, which, like S. saussurei has striate mandibles, is larger, has a wider head, and flat eyes without a white layer. The smaller species Sericomyrmex parvulus and Sericomyrmex 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. 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.

Distribution
Ješovnik & Schultz (2017) - Bolivia, Brazil, Ecuador, French Guiana, Guyana, Peru, Suriname, Trinidad and Tobago, Venezuela.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Guyana , Trinidad and Tobago.

Biology
Castano-Meneses et al (2017) - The springtail species Cyphoderus agnotus Börner (Cyphoderidae: Cyphoderus), Cyphoderus similis Börner (Cyphoderidae: Cyphoderus) and Proisotoma minima (Absolon) (Collembola: Isotomidae) are known from nests of this ant.

Morphology
Ješovnik & Schultz (2017) - 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, 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. 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, but which is absent in males and in callow workers, as well as in some individuals of Sericomyrmex maravalhas. Why this layer extends to and completely covers the eyes in some species but not others remains unknown.

Castes
Jesovnik and Schultz 2017. Figure 56. S. saussurei worker; head, profile, and dorsal view. Striate-mandibled form (USN-MENT01125217) (a, c, e). Smooth-mandibled form (USNMENT01125221) (b, d, f). Figure 57. S. saussurei worker (USNMENT01126237), SEM images. a Head, full-face view b mandibles c mesosoma, lateral view d metasoma, lateral view e eyes completely covered with white layer, individual ommatidia not visible f eyes with thick white layer, ommatidia visible through small holes in the layer.

Jesovnik and Schultz 2017. Figure 58. S. saussurei queen and male; head, lateral profile, and dorsal view. Queen (USNMENT01125514) (a, c, e) Male (USNMENT01125515) (b, d, f). Figure 59. S. saussurei larva (USNMENT01126236), SEM images. a Lateral view b ventral view c head, frontolateral view d head, dorsal view e mouthparts f anal setae.

Nomenclature

 *  saussurei. Sericomyrmex saussurei Emery, 1894c: 223 (w.) BRAZIL.
 * Ješovnik & Schultz, 2017a: 96 (l.).
 * Status as species: Forel, 1895b: 142; Forel, 1912e: 191 (in key); Wheeler, W.M. 1916c: 11 (in key); Emery, 1924d: 339; Borgmeier, 1927c: 128; Kempf, 1972a: 229; Bolton, 1995b: 382; Ješovnik & Schultz, 2017a: 92 (redescription).
 * Senior synonym of burchelli, impexus, maracas: Ješovnik & Schultz, 2017a: 92.
 * burchelli. Sericomyrmex burchelli Forel, 1905b: 183 (q.m.) BRAZIL.
 * Status as species: Forel, 1912e: 191 (in key); Wheeler, W.M. 1916c: 10 (in key); Emery, 1924d: 339; Borgmeier, 1927c: 127; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of saussurei: Ješovnik & Schultz, 2017a: 92.
 * impexus. Sericomyrmex impexus Wheeler, W.M. 1925a: 54 (w.) GUYANA.
 * Status as species: Weber, 1946b: 142; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of saussurei: Ješovnik & Schultz, 2017a: 92.
 * maracas. Sericomyrmex urichi subsp. maracas Weber, 1937: 395, fig. 7 (w.q.m.) TRINIDAD.
 * Subspecies of urichi: Weber, 1945: 44; Kempf, 1972a: 230; Bolton, 1995b: 382.
 * Junior synonym of saussurei: Ješovnik & Schultz, 2017a: 92.

Ješovnik & Schultz (2017):

Worker
(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 to abruptly impressed. Vertexal impression and frontal tumuli distinct. Mandible with 7–8 teeth, dorsally glossy and striate, sometimes striation reduced or absent. 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, 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.

Queen
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.

Male
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.

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.

Type Material
Holotype worker: Brazil, Mato Grosso, [-13, -56], ANTC25804, 1886, P. Germain (: 1w, USNM00445513).

References based on Global Ant Biodiversity Informatics

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 * Wheeler W. M. 1925. Neotropical ants in the collections of the Royal Museum of Stockholm. Arkiv för Zoologi 17A(8): 1-55.