Strumigenys argiola

From Fellner et al 2007: The distribution area of P. argiola is centred around the Mediterranean basin (Bernard, 1968), which implies that it is a thermophilic species mainly of open landscapes (see localities in southern Switzerland and Hungary). In Switzerland, for example, P. argiola was found in calcareous lean grassland (canton Jura) and in a dry pine forest (Pfynwald, canton Wallis). The new records from the extreme east and south of Austria fit rather well into the known distributional pattern: the nearest records approximately 200 km to the east of Lower Austria are from Central Hungary and the records from Carinthia parallel those from the southern Alps in Switzerland. As detailed above, the Austrian localities are also characterized by rather warm microclimatic conditions during the vegetation period.

Lapeva-Gjonova, & Ljobomirov (2020) note that while Strumigenys tenuipilis occurs in a wide variety of preserved natural habitats, S. argiola is common in highly disturbed environments as well as urban and suburban open habitats (Holecová et al., 2015).

Identification
A member of the argiola complex in the Strumigenys argiola group.

Distribution
This species is unusual for a Strumigenys in its occurrence in southern Europe.

Holecová et al. (2015) report that S. argiola is a thermophilic species significantly preferring open landscapes. Records from Slovakia confirmed this fact. Cryptic ant species are difficult to detect with common sampling methods used in myrmecology. We expect that further localities from southern parts of Slovakia will be recorded on dry grassland sites. S. argiola is a native but long overlooked memeber of the Slovak ant fauna.

Distribution based on Regional Taxon Lists
Palaearctic Region: Austria, Azerbaijan, Balearic Islands, Bulgaria, Croatia, France, Greece, Hungary, Iberian Peninsula, Israel, Italy, Portugal, Russian Federation, Slovakia, Spain, Switzerland, Tunisia, Turkey.

Biology
Brown (1949) - Apparently this species accepts drier and more open situations than do most other dacetines; in this respect argiolus seems to be similar: to Strumigenys baudueri and Strumigenys membranifera, which apparently have similar ranges in the Mediterranean area. It would not be surprising if argiolus were found to occur in southeastern North America or other New World localities with a warm, dry climate. No observations on the feeding habits of this species have been reported. Emery states that the nests are small and "subterranean." The male linked doubtfully with this species was taken separately in August.

Nomenclature

 *  argiola. Epitritus argiolus Emery, 1869a: 136, fig. 1 (q.) ITALY. Emery, 1875a: 75 (w.); Emery, 1875b: 473 (w.); André, 1883b: 404 (m.). Combination in Strumigenys: Baroni Urbani, 1998: 163; in Pyramica: Bolton, 1999: 1672; in Strumigenys: Baroni Urbani & De Andrade, 2007: 115. Senior synonym of barbara: Brown, 1949b: 44. See also: Kutter, 1977c: 168; Bolton, 2000: 288.
 * barbara. Epitritus argiolus var. barbara Santschi, 1923a: 136 (w.) TUNISIA. Junior synonym of argiola: Brown, 1949b: 44.

Worker
Bolton (2000) - TL 1.8-2.1, HL 0.46-0.50, HW 0.40-0.46, CI 89-93, ML 0.16-0.20, MI 35-40, SL 0.20-0.23, SI 50-52, PW 0.24-0.28, AL 0.50-0.55 (15 measured).

Among the sparse dacetine species of the West Palaearctic argiola is very distinctive because of its elongate narrow mandibles with spiniform apicodorsal tooth and orbicular cephalic pilosity, contrasting strongly with the other species, which are members of the baudueri- and membranifera-groups. Too much reliance should not be placed on the 4-segmented antennae of argiola as an identification character because this feature is duplicated in many West Palaearctic samples of species in the baudueri-group. Sub-Saharan Africa has seven species in the group (discussed under Strumigenys laticeps, below). S. argiola differs from all the Afrotropical species as follows.

1 No large subbasal lobe on the broad flattened scape.

2 Hairs on the leading edge of the scape curved or inclined toward the apex of the scape.

3 Four (very rarely 3) preapical denticles on each mandible.

4 No long strap-like or filiform hairs on the anterior clypea1 margin.

5 Postpetiolar spongiform lobes large.

6 Head relatively narrow (CI < 1 00).

7 First gastral tergite smooth or at most with weak superficial reticulation.

All the Afrotropical taxa have a large and strongly developed subbasal lobe on the scape, have hairs on the leading edge of the scape that are erect or directed toward the base of the scape, have 0-2 preapical denticles, have 4-6 long anteriorly directed strap-like or filiform hairs on the anterior clypeal margin, have postpetiolar spongiform lobes that are very small or absent, have relatively broad heads (CI at least 1 00), and have the first gastral tergite strongly reticulate-punctate.

The five species of the Strumigenys argiola group. that occur in the East Palaearctic and Oriental regions (Strumigenys hexamera, Strumigenys hirashimai, Strumigenys lachesis, Strumigenys sinensis, Strumigenys tisiphone) all have 6 antennal segments (although funicular segments 2 and 3 are very reduced in Strumigenys lachesis), as opposed to the 4 seen in argiola; also all have fewer than 4 preapical denticles on each mandible and have dense orbicular pilosity on the promesonotal dorsum.

S. argiola was redescribed in detail by Brown (1949a). Its circum-Mediterranean distribution is noted in Emery (1916), Brown (1949a) and Bernard (1967). More recently it has also been found in Spain (Espadaler, 1979), Switzerland (Kutter, 1977), Azerbaij an and Georgia (Arakelian & Dlussky, 1991), and Germany (Behr, Lippke & Colln, 1996); its presence in the Balkans was confirmed by Agosti & Collingwood (1987). It does not appear to penetrate the Afrotropical region (Bolton, 1983 and present study).

Brown (1949) - Best figured by Emery in 1917 (op. cit.) for head and mandibular characters. Specimens sent me by Sr. Mario Consani of Florence show the following measurements: maximum measurable length of head proper, 0.46 ± .005 mm, exposed length of mandibles, 0.18 ± .003 mm., length of alitrunk, 0.50 ± .01 mm., total length, 2.05-2.15 mm., cephalic index, 92-93, mandibulo-cephalic index, 39-40. (Two specimens taken at Ancona by Dr. A. Andreini.) I have also seen four specimens in the collection of Dr. W. M. Mann which agreed closely with my specimens. Emery, who had a considerable number of specimens before him in 1917, gave the range of the length in the worker as 1.8-2.2 mm.

The mandibles, just distad of the long, sharp subapical spinelike tooth which each bears on its inner border, are slightly thickened and bent sharply ventrad and somewhat posteriorly, so that in side view they resemble a stout, slightly recurved hook protruding from the mouth region. The masticatory border of each recurved apical section bears six or so minute, serially arranged denticles, the apicalmost being larger, more acute and toothlike. Basad of the long spine, each mandible bears on its inner border four small, separated, serially arranged acute teeth which alternate shorter-longer, beginning just basad of the spine with a shorter one. Emery shows this more or less correctly in his figure (1917, fig. 64), but the dentition is best shown on the right mandible, while that of the left is obscure and sketchy. Basad from these are several spatulate hairs.

The long labral lobes and the angulate anterolateral borders of the occipital lobes are shown clearly in Emery's figure just cited, but my specimens have the antennal scapes slightly more incrassate. The cephalic hairs are much like those on the dorsum of the head of Smithistruma pergandei; that is, with a short petiole and a suborbicularly flattened apical portion bent at right angles to the petiole so as to lie parallel with and close to the integumental surface.

Other characters which have received little notice in former descriptions and figures are noted for my specimens and those in the Mann collection: The mandibles with a basal border running obliquely under the clypeus at full closure, this border separated from the apical (inner or masticatory) border by an obtuse angle probably representing a reduced basal tooth. The apical border has two margins, an upper or dorsal and a lower one; the prespinal teeth and denticles and the long spiniform tooth itself borne on the dorsal of these two margins; the space between these margins in the form of a shallow convex groove with a median ridge.

Pronotum depressed above and nearly plane, but not definitely marginate laterally. The mesonotum drops off rather suddenly at its rounded posterior border to meet the dorsum (base) of the propodeum, the latter sloping sharply (at an angle of 45° from the general dorsal thoracic plane) to meet the vertical propodeal declivity. Propodeal teeth very small but rather acute, each subtended ventrally by a thin lamella which is slightly widened ventrally. Alitrunk in profile very weakly convex from the anterior pronotal margin to the posterior mesonotal margin.

Petiole with a fairly long, anteriorly tapering peduncle; node seen from above globular, only half as long and less than half as wide as the postpetiolar node, its spongiform appendages obsolete. Postpetiolar node transverse-oval, relatively bulky, with only a rather sparse growth of spongiform appendages, and these restricted to the posterior borders.

Hairs on dorsum of alitrunk and of the two nodes extremely few and scattered, squamiform to varying degrees; gastric dorsum with scattered, fine, short, erect hairs, most of which are weakly flattened at their tips.

Sculpture of head and alitrunk minutely punctulate-granulose, much like that of ordinary Smithistruma and Strumigenys species; nodes also similar, appearing opaque to subopaque; basal costulae of first gastric segment few and widely spaced, long on the sides and shorter in the middle; first gastric segment dorsally with what appears to be faint pebble-shagreening, but rather strongly shining. This effect may be due to a thin coat of the. Secretions with which dacetines often cover themselves, but there definitely seems to be some sort of feeble sculpture present, at least in the Ancona specimens.

Color yellowish to medium ferrugineous.

Queen
Brown (1949) - Emery gives the total length as 2.2 mm. and the length without the mandibles as 2 mm. and describes the alitrunk as “subtilius, longitudinaliter coriaceo-rugulosus.” There appears to be little or no difference in proportion between the female and large workers except the usual ones in the case of thoracic development and possibly in the greater bulk of the gaster.

Male
Brown (1949) - The male which Andre associated with this species has not, to my knowledge, actually been taken with workers or females. It could be the male of Smithistruma baudueri, with which another male has been uncertainly identified, or of Trichoscapa membranifera, for which no male is known, or it could belong to an undescribed dacetine species, the workers or females of which have not yet been found.

Type Material
Holotype queen (dealate), ITALY (Haliday) [examined].

Determination Clarifications
Bolton (2000) - A recent record of this species from Switzerland (Borcard, Borcard, et al., 1997) is a misidentified queen of baudueri (Baroni Urbani, 1998).

References based on Global Ant Biodiversity Informatics

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