Stenamma zanoni

Nothing is known about the biology of .

Identification
Rigato (2011) - A relatively large taxon, with moderately elongate scapes, and several standing hairs on tibiae and scapes. The worker has short and stout, somewhat upturned propodeal teeth. The male has about the same pilosity as in the worker and has notauli almost absent.

An easily distinguished taxon. Its size is close to petiolatum, with which it may be superficially confused (e.g. Della Santa, 1988, and see below); yet the only strong similarity between them is the presence of raised hairs on tibiae and scapes. Other diagnostic features, such as SI, promesonotal sculpture, propodeal teeth and waist shape are strikingly different.

I borrowed the worker reported by Della Santa (1988) as Stenamma petiolatum and when I received it and several other Swiss Stenamma collected from close localities, I was surprised to find that his specimen and another one actually belonged to my new taxon, of which I had just few workers from Northeast Italy, quite far from Switzerland.

I confidently assign to S. zanoni the male that Kutter (1971) described as belonging to S. petiolatum, and a male I have from North Italy (Monza park) is also included. Initially, I thought these two males could belong to different taxa because Kutter’s figures show a relatively high propodeum with basal and declivitous faces very similar in length, whereas my own specimen has the basal propodeal face about twice as long as the declivity. I examined Kutter’s male (borrowed from MZL), and realized that Kutter’s figure is somewhat inaccurate. His male is very similar to mine and must be considered as conspecific with it.

The male of S. zanoni is strikingly different from any other known European Stenamma male because of its virtually absent notauli, which are well developed in all other taxa. Also, Kutter (l.c.) correctly pointed out the relatively strong development of mid and hind legs’ tibial spurs in his “S. petiolatum” male. In fact his male, as well as the worker, has relatively well developed spurs when compared with other taxa, but in my male from “Monza park” the spurs are less developed. However, this is not considered a fully reliable feature for separating taxa, both for lack of sufficient material and for some variations I observed among females and males of other Stenamma. Mid and hind tibial spurs in most Stenamma I examined are reduced and often hardly visible, or even appear completely lacking (e.g. in Stenamma striatulum): they are short and thin at most and easily confused with the pilosity of the tibial apices. About this feature Branstetter (2009) reported for Stenamma’s worker caste: “middle and hind tibiae lacking spurs” (character 17, page 43). I propose to modify this statement to: “middle and hind tibial spurs variable, usually reduced or absent”.

Distribution based on Regional Taxon Lists
Palaearctic Region: Italy, Switzerland.

Castes
Queens have yet to be collected.

Nomenclature

 *  zanoni. Stenamma zanoni Rigato, 2011: 15, figs. 7, 14, 22, 29, 36, 62, 67, 72 (w.m.) ITALY.

Worker
Holotype. TL 4.3; HL 1.00; HW 0.81; CI 81; SL 0.80; SI 99; PCI 25; PnW 0.57; AL 1.23; PSI 1.24; PeL 0.44; PPL 0.24; PeH 0.25; PPH 0.25; PI1 55; PI2 54; MTL 0.72; TI 89; PeW 0.18; PPW 0.24.

TL 4.2–4.7; HL 0.94–1.02; HW 0.77–0.84; CI 80–84; SL 0.73–0.82; SI 95–99; PCI 27–31; PnW 0.52–0.59; AL 1.21–1.30; PSI 1.19–1.64; PeL 0.42–0.46; PPL 0.23–0.25; PeH 0.24–0.25;  PPH 0.24–0.26; PeW 0.17–0.20; PPW 0.22–0.25; PI1 51–57; PI2 52–56; MTL 0.68–0.75; TI 85–90 (7 measured).

Mandibles 9-10 toothed, longitudinally rugose with distinct piligerous pits. Anterior clypeal border shallowly concave in the middle; posterior clypeal lobe about 1/4 or more as wide as the frontal lobe distance. Head distinctly longer than wide with moderately convex sides, narrower at occipital angles than at mandibular insertion; mostly areolate with longitudinal rugulation, especially medially, and a quite well developed reticulate-punctate ground sculpture. Scape moderately long, reaching or at most hardly surpassing the posterior margin of the head when laid back. Posterior margin of the head straight. Eye with some 10 or less ommatidia.

Pronotum anteriorly transversely rugulose. Promesonotal surface largely irregularly longitudinally rugulose and with very weak ground sculpture, except laterally where it is more developed. Mesopleuron mostly reticulate-punctate with superimposed irregular rugulation. Mesosoma in profile with promesonotum forming a very shallow convexity; metanotal groove V-shaped, the propodeal dorsum rises steeply from it into a flat dorsal face. Propodeum dorsally and laterally mostly irregularly areolate with reticulate-punctate ground sculpture; declivity smooth and shining. Propodeal teeth strong and short, when more developed they are distinctly upturned. Waist finely reticulate-punctate with some scattered short irregular rugulae; nodes appearing mostly smooth and shining. Petiole with a relatively narrowly domed node, its sternite distinctly concave at node level and with a vestigial anterior subpetiolar process. Postpetiole in profile relatively short and high; its sternites faintly concave and with a slightly protruding anterior process. In dorsal view petiole nearly as wide at the level of the spiracles as at the node.

Pilosity mostly as in other species dealt with in this paper; but extensor surface of tibiae and dorsal surface of scapes bear few to several subdecumbent to suberect hairs that are raised above the level of the pubescence. Such hairs do not always clearly project beyond the pubescence.

Colour chiefly brown, with a more or less developed ferrugineous tinge and chiefly testaceous legs, antennae, clypeus and mandibles. Gaster slightly paler than the remaining body, except for most of the first tergite.

Male
TL 4.3–4.6; HL 0.68–0.77; HW 0.57–0.65; CI 84; SL 0.33–0.36; SI 55–58; AL 1.38–1.50; ScW 0.65–0.73; MnL 0.94–1.06; PeL 0.47–0.50; PPL 0.25–0.27; PeH 0.20–0.25; PPH  0.21–0.25; PeW 0.16–0.20; PPW 0.23–0.27; PI1 53–54; PI2 77–82; MTL 0.93–1.04; TI 160–163 (2 measured).

Mandibles fully developed, 6-toothed, superficially finely striolate and shining. Head in full face view with weakly convex sides and straight posterior margin; its surface finely reticulate-punctate with superimposed, mainly longitudinal and irregular rugulation. Pronotum rugulose with weak ground sculpture. Mesoscutum with vestigial notauli. Mesonotum longitudinally rugulose, except laterally. Sides of mesosoma mostly reticulate punctate; mesopleuron smoother, propodeum with rougher sculpture and partially rugose. Propodeal dorsum very superficially reticulate-punctate and about as shiny as the declivity. In profile propodeal dorsum about twice as long as the declivity. Petiole and postpetiole mostly finely reticulate-punctate, except for their nodes, which are smooth or nearly so. Waist sternites at most weakly concave in profile; postpetiole with a small protruding point anteriorly.

Pubescence mostly decumbent and especially abundant on the appendages, standing hairs sparse and mostly abundant on mesonotum and gaster. Some subdecumbent hairs occur on the outer edge of the tibiae.

Colour dark blackish brown; legs mostly brown, antennae brown with last 5 joints pale testaceous, mandibles testaceous.

Type Material
Holotype (worker): ITALY, FRIULI VENEZIA GIULIA, Osoppo (Udine), 30.iv.2001, excavation nr. fortress (D.Zanon)

Paratypes. 5 workers with the same data as the holotype (MSNM). 1 male: ITALY, LOMBARDIA, Monza park (Monza-Brianza), 25.ix.1985 (F. Rigato) (MSNM). 1 worker: SWITZERLAND, CANTON TICINO, Calonico-Leventina, 950 m (A. Focarile) [original labels: HELVETIA (Ticino) Calonico-Leventina, 950 m A. Focarile/Castanetum insubricum] ; 1 worker: SWITZERLAND, CANTON TICINO, Piccola Isola di Brissago, 12-19.vii.1986 (E. Della Santa) [original label: SUISSE – Tessin, P.te île Brissago, 12-19.7.86, E. Della Santa] (MHNG). 1 male: SWITZERLAND, CANTON TICINO, San Nazzaro, 30.ix.1962.