Sphinctomyrmex stali

Recent collections suggest that this species can be most commonly found in submontane forests (above 600m) of the states of Santa Catarina and Sao Paulo, from whence come most of the specimens in collections. In a single leaf-litter sample collected in Sao Bonifacio, Santa Catarina, six workers and two ergatoids, very similar to the workers, were captured, which suggests that S. stali is polygynous, as already described for other Sphinctomyrmex species. (Feitosa et al. 2012)

Identification
Feitosa et al. (2012) - The distinctly elongate head, the narrow insertion of the clypeus between the frontal lobes, the absence of lateral lobes from the anteriormargin of clypeus, and the absence of appressed hairs on the dorsum of gaster separate S. stali from Sphinctomyrmex schoerederi. This species can be separated from Sphinctomyrmex marcoyi by its much larger size and the absence of a median smooth longitudinal stripe on the dorsum of mesosoma.

Variation: At least three different morphotypes of this highly variable species can be distinguished. Categorization of these morphotypes is somewhat arbitrary as they are not entirely distinct from each other. Therefore, they are not to be recognized as distinct units, but rather as belonging to a gradient. The following comparison, however, simplifies the description of morphological variation and allows for the recognition of possible geographic patterns.

Morphotype 1. Medium size (HW 0.48–0.55, TL 3.51–4.00). Color reddish-brown to blackish. Posterior area of head (nuchal area) predominantly smooth and shiny. Head distinctly longer than broad (CI 75.50–81.40), with lateral margins weakly convex; eyes reduced but distinctly larger than the adjacent foveae of head surface. Promesonotal suture distinct in dorsal view.

This morphotype conforms most closely with the first workers described for this species. Despite its distribution being restricted to scattered localities in the state of Santa Catarina, southern Brazil, it is the most common morphotype of S. stali in museum collections.

Morphotype 2. Large size (HW0.60–0.69, TL 4.05–4.64). Color reddish to dark brown. Posterior area of head (nuchal area) predominantly smooth and shiny. Head moderately longer than broad (CI 81.63–86.00), with lateral margins weakly convex; eyes reduced but distinctly larger than the adjacent foveae of head surface. Promesonotal suture variably impressed in dorsal view.

In his initial description of S. stali workers, the author stated: “. . .The specimens collected in October 3, 1953 are somewhat larger than the other. . .” We examined these workers mentioned by Borgmeier; in fact, they are considerably larger than the other workers, and even larger than the ergatoids examined here. However, except for the exceptional size, the individuals of this morphotype are very similar to those ofmorphotype 1. Additional workers of morphotype 2 were collected in the Brazilian states of Bahia, Minas Gerais, and Sao Paulo.

Morphotype 3. Small size (HW 0.44–0.47, TL 3.33–3.41). Color pale yellow to reddish-brown. Posterior area of head (nuchal area) irregularly striate, with sparse punctures. Head notably longer than broad (CI 71.79–75.00), with lateral margins subparallel; eyes vestigial, feebly convex; in some cases only discernable by a dark spot on the sides of head, of the same size as the adjacent foveae of the head surface. Promesonotal suture obsolete, almost indistinct in dorsal view.

This is the most distinctive morphotype of S. stali, known so far only from Vicosa, state of Minas Gerais, southeastern Brazil where it occurs in sympatry with S. schoerederi.

Key to Sphinctomyrmex of the Neotropics

Distribution
Sphinctomyrmex stali is known from sparse localities along the southeastern portion of the Brazilian Atlantic Forest, from Santa Catarina to southern Bahia.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Biology
Feitosa et al. (2012) - Mayr described Sphinctomyrmex with S. stali as its type species, based on a single dealate gyne. However, except for the holotype, there are no records of normal (alate) gynes for S. stali. All reproductive females collected after the original description are ergatoids. Dr. H. Vardal, Hymenoptera curator of the NHRS collection, kindly sent us images of the S. stali holotype. We confirm that it is a typical dealate ant gyne given the wing scars and the structure of mesosoma. Therefore, there are at least three possibilities: (1) Sphinctomyrmex stali can possess both forms of reproductive females, alates and ergatoids, as already recorded for other ant species; (2) our current conception of S. stali includes more than a single species, not entirely distinguishable by morphology, and each species may present a different gyne form, or (3) the initial suspicion by Brown (see below) may prove correct, and the Brazilian locality record for the dealate gyne designated as holotype by Mayr may be in error. Hypotheses 1 and 2 seem to be the more plausible based on the label information of the type specimen. The collector of the type, the Finish entomologist Reinhold Ferdinand Sahlberg, probably captured this specimen while collecting insects in his visit to Rio de Janeiro in the middle 1800’s [R.F. Sahlberg’s field book; Hege Vardal (pers.com.)]. Incidentally, this possibility is supported by Kempf ’s decision to treat Rio de Janeiro as the type locality of Sphinctomyrmex stali. The nature of S. stali reproductive females will only be solved with the collection of additional material associated with workers.

In correspondence between William Brown Jr. and Father Thomas Borgmeier in 1954 [2], Brown mentions: “The thing that really surprised me about the paper was your mention of Plaumann’s discovery of Sphinctomyrmex in Santa Catarina! As matter of fact, I have just finished examining the type of S. stali [SIC] Mayr (Stockholm Museum), and just send it back to Sweden. I had concluded that the Brazilian locality must be in error, but if your specimens are the same, then I must revise my opinion! I could discover no characters of generic significance between S. stali and the known winged females of certain Australian Notosphinctus, and I tentatively conclude that these two names are synonyms. I have seen the type of furcatus Emery, from Burma, and also a winged female of a species (undescribed?) marked as from “Sierra Leone/Afzelius” which is surely of the same genus as stali on female characters alone, but which is blackish in color. . ..”

Castes
Males have yet to be collected.

Nomenclature

 *  stali. Sphinctomyrmex stali Mayr, 1866b: 895, pl. 20, fig. 8 (q.) BRAZIL. Borgmeier, 1957: 105 (w.). See also: Feitosa, Brandão, et al. 2011: 5.

Worker
Feitosa et al. (2012) - (n=20) HL (0.60–0.79); HW(0.44–0.68); SL (0.31–0.50); EL (0.02–0.08); WL (0.71–1.12); PL (0.28–0.43); PW (0.29–0.41); GL (1.66–2.39); TL (3.33–4.64); CI (71.79–86.00); SI (68.42–77.50); OI (3.33–12.50).

Size highly variable (TL 3.33–4.64). Body yellowish to black, commonly reddish-brown with slightly lighter appendages. Pilosity dense; gaster devoid of appressed pilosity. Posterior area of head (nuchal area) smooth to coarsely striate; dorsum of body sparsely foveolate; space between the foveae predominantly smooth and shiny; declivous face of propodeum smooth and shiny to shallowly punctuate-reticulate; sides of meso- and metasoma predominantly smooth and shiny, with a few coarse punctures. Head slightly to considerably longer than broad, (CI 71.79–86.00); lateral margins subparallel to gently convergent; clypeus narrowly inserted between the frontal lobes, so that the frontal carinae are close to each other; lateral lobes of the anterior margin of clypeus absent or vestigial; antennal scape apices not reaching the level of the compound eyes; apical segment of antennae as long as the three preceding sgments combined; antennal club formed by the apical segment or by the two apical segments; compound eyes strongly reduced to vestigial, as large as or slightly larger than the adjacent foveae of head surface. In dorsal view, lateral margins of mesosoma subparallel; pronotum with humeral corners angled but not forming teeth or spines; promesonotal suture distinct to vestigial in dorsal view, not impressed. In dorsal view, petiole as long as to gently longer than broad with lateral margins feebly divergent; subpetiolar process well developed. Abdominal segments IV to VII with relatively short pretergites, separated from each other by deeply impressed, short constrictions.

Queen
Feitosa et al. (2012) - (Ergatoid) (n = 3). HL (0.66–0.68); HW (0.52–0.55); SL (0.36–0.38); EL (0.08–0.11);WL (0.91–0.98); PL (0.36–0.41); PW (0.32–0.36); GL (1.95–2.17); TL (3.89–4.20); CI (78.57–81.40); SI (65.71–72.73); OI (15.15–20.00).

Two forms are recognized, alates and ergatoids (but see comments below). The alate form is known from a single specimen, the holotype. This gyne differs from workers by the typical characters expected for ant reproductive females: size significantly larger (TL ca. 6.00); ocelli well developed; compound eyes considerably large, occupying almost one third of the lateral margin of head. Pronotumis well developed, without projections; scutum large and trapezoidal; notauli shallow, almost indistinct; parapsidial lines feebly visible and convergent towards scutellum; scutoscutellar sulcus impressed; scutellum relatively narrow and set at the same level as the scutum, in lateral view; propodeum large in dorsal view, with dorsal face meeting the declivous face in a blunt angle; wings unknown. Petiole and gaster comparatively larger than in conspecific workers. The ergatoids differ from the conspecific workers only by the presence of three equally developed ocelli and by the compound eyes being comparatively well developed (OI 15.15–20.00).

Type Material
Feitosa et al. (2012) - Holotype gyne: Brazil, Rio de Janeiro, F. Sahlberg coll., HEVA000000012 (high-resolution images examined)

Etymology
Feitosa et al. (2012) - Dr. Gustav Mayr named this species after the Swedish entomologist Dr. Carl Stal (1833–1878), who was a professor of the Zoological Department of the Royal Swedish Museum of Natural History in Stockholm. Although he published mostly on Hemiptera and was regarded as its world’s foremost scholar, Dr. Stal also published on Orthoptera and to a lesser extent on Coleoptera and Hymenoptera.