Aphaenogaster trinacriae

This species was mostly collected in natural Quercus forest but occasionally also in some artificial Pinus forest. All sites were either fully established forest or degraded forest. Altitude between 110 m and 1,260 m. Aphaenogaster trinacriae partly shares its distribution with that of Aphaenogaster ichnusa, whose ecology requirements are seemingly vastly overlapping (SCHIFANI & ALICATA 2018), therefore competition between these two may be expected to be significant. On the contrary, A. subterranea s. str. is found at higher altitudes and/or in different habitats in Sicily (SCHIFANI & ALICATA 2018). Aphaenogaster trinacriae was reported removing elaiosomes from seeds of Euphorbia characias (LI VIGNI 2014, subspecies A. sicula).

Identification
Alicata and Schifani (2019) - Worker. Aphaenogaster trinacriae is characterized by ferruginous color of the body except for the very dark gaster and potential presence of dark area on the frons. Among the sympatric species this pattern can only be confused with some individuals of Aphaenogaster ichnusa or Aphaenogaster sicula. Aphaenogaster subterranea ichnusa can be easily distinguished by the marked metanotal groove in lateral view, less sculptured pronotum and different shape of the mesonotum. Aphaenogaster sicula tends to have darker head compared to the thorax and it is overall much less sculptured. Moreover, it presents a very reduced promesonotal suture, which on the contrary is very well marked in Aphaenogaster trinacriae. The shape of the mesonotum and its sculpture easily separate Aphaenogaster trinacriae from any other similar Maghrebian congeneric species. Male. Only some of the Aphaenogaster males present mesosoma with an anterior gibbous part and a comparatively fl at posterior part like Aphaenogaster trinacriae. Among the sympatrics pecies that do so, Aphaenogaster splendida can be easily distinguished by different shape of the metathorax, forming a decisively slenderer area in front of the propodeum in lateral view (see EMERY 1908; 1916). Aphaenogaster sardoa male is larger, its metathorax does not form a slenderer part in front of the propodeum, it possesses a visibly less gibbous anterior part and much more abundant erect setae on the body. Aphaenogaster fiorii and Aphaenogaster sicula are the most similar, but do not possess the well developed enlarged flat areas on the sides of the propodeum (better observed in dorsal view). In addition, Aphaenogaster fiorii is much lighter and presents more developed and differently shaped tubercles on the propodeum. The shape of the mesosoma also distinctively separates Aphaenogaster trinacriae from the somewhat similar Maghrebian species: Aphaenogaster crocea, Aphaenogaster faureli, Aphaenogaster mauritanica, Aphaenogaster nadigi, Aphaenogaster strioloides, Aphaenogaster theryi.

Queen. Among sympatric species the mesosoma shape is only similar to that of Aphaenogaster fiorii, Aphaenogaster sicula and Aphaenogaster subterranea However, Aphaenogaster fiorii is chromatically very different, and both Aphaenogaster fiorii and Aphaenogaster sicula possess thicker spines. Aphaenogaster subterranea appears to be very similar but it is usually darker and possesses more rectangular head with more parallel sides in frontal view. The scarcity of available information does not allow a proper comparison with the Maghrebian forms.

Distribution
Alicata and Schifani (2019) - Aphaenogaster trinacriae has a small range, being exclusively limited to Sicily, where it is most abundant in its Western regions and completely absent in its North Eastern regions: in Etna, Nebrodi and Peloritani mountains the same habitats are occupied only by the ecologically similar Aphaenogaster ichnusa, and very rarely by Aphaenogaster fiorii. Aphaenogaster trinacriae was also found in Favignana, a sedimentary island belonging to the Egadi Islands, which is about 7 km distant from the Western Sicilian coast and was alternately connected by land to Sicily in the past (Agnesi et al. 1993).

Distribution based on Regional Taxon Lists
Palaearctic Region: Italy.

Habitat
Aphaenogaster trinacriae appears to have a well-defined habitat specificity mainly linked to thermophilous broad-leaved forests. Its abundance within the relatively small distribution range must have been severely reduced due to the past deforestation (La Mantia 2009). Many sites in which the species is found are habitat patches likely too distant from each other to allow the species dispersal from one patch to another, resulting in presumably complete isolation of these populations. Although reforestation projects have increased the forested surface in Sicily, they may have not necessarily helped the species to recover the lost habitats. Aphaenogaster trinacriae has never been found in Eucalyptus reforestations, and reforestation patches of other kind may sometimes be too isolated to be colonized. It would be worth investigating if the abundant presence of Aphaenogaster ichnusa in some isolated reforested areas, in which Aphaenogaster trinacriae is absent despite seemingly adequate ecological conditions, is due to the lower dispersal capacity of the latter or unintentional introductions of the former.

Biology
Alicata and Schifani (2019) - Monogynous. No more than one queen per colony detected in the wild, attempts to found colonies in captivity with multiple queens only resulted in monogynous colonies.

Phenology. Winged sexuals were collected in nests in Bosco della Ficuzza (PA) during the last week of July and in C. da Sugherita, M. Sambughetti-Campanito (EN) in August. In captive colonies, sexuals began to leave the nest from the second week of July to the first week of August, but no attempt to form an actual nuptial flight was detected (Alicata 1999). In the wild, it can be speculated that nuptial flights may start with the first relevant rains at the end of summer.

Myrmecophiles. Six individuals of Scydmaenus rufus Müller & Kunze, 1822 (Staphylinidae, Scydmaeninae) were collected inside a nest of Aphaenogaster trinacriae in Bosco della Ficuzza (PA) during December.

Nomenclature

 *  trinacriae. Aphaenogaster trinacriae Alicata & Schifani, 2019: 10 (w.q.) ITALY.

Worker
Holotype worker: HL: 1.25; HW: 1.07; CI: 85.60; FW: 0.92; SL: 1.22; SI: 114.01; MW: 0.7; ML: 1.65: Measurements and indices (89 individuals, 14 localities; including holotype): HL: 1.16 ± 0.05 (0.97–1.27); HW: 1.01 ± 0.07 (0.77–1.17); CI: 87.14 ± 2.81 (79.48–92.15); FW: 0.87 ± 0.06 (0.70–1.00); SL: 1.17 ± 0.04 (1.05–1.27); SI: 115.59 ± 5.24 (106.38–135.48); MW: 0.64 ± 0.04 (0.52 ± 0.75); ML: 1.52 ± 0.08 (1.27–1.70). Whole body ferruginous (yellowish in freshly emerged workers), except for dark gaster. Central area of frons, scapi and femora are in some cases also darker than rest of head. Head subrectangular, lateral margins under eyes slightly rounded, posterior margin of head straight. Anterior margin of clypeus gradually convex, mandibles rounded. Antennae with twelve segments, antennal club with four segments. Promesonotal suture well-marked, creating clear discontinuity of dorsal profile in lateral view. In lateral view, dorsal profile of metanotum is rounded, dorsal profile of propodeum mostly straight, spines are variable in size and orientation, but are often horizontal. Sculpture relatively well developed in general. Head reticulated, with longitudinal striae almost reaching occiput, strongly developed especially under and around eyes, and present on mandibles. Mesepisternum and propodeum reticulated with fine longitudinal striae, pronotum finely imbricate, gaster smooth, petiole and postpetiole finely imbricate to reticulate. Suberect and erect setae sparse over head, decumbent setae on mandibles, adpressed setae on scapes and adpressed to subdecumbent setae on flagellomeres. Long setae extending down from clypeus. Erect setae all over dorsal surface of mesosoma, petiole and postpetiole, and all over gaster. Mostly adpressed, partly suberect setae on legs, with sparse erect setae on coxae and femora.

Queen
(4 individuals, 3 localities): HW: 1.36 ± 0.01; HL: 1.29 ± 0.02; CI: 94.52 ± 0.01; FW: 1.12 ± 0.00; SL: 1.23 ± 0.01; SI: 95.18 ± 1.03; MW: 1.25 ± 0.03; ML: 2.36 ± 0.04. Whole body ferruginous, some lighter bands on gaster. Head subrectangular, lateral surface below eyes rounded, posterior margin of head straight. Anterior margin of clypeus slightly convex, mandibles rounded. Antennae with twelve segments, antennal club with four segments. Pronotum rounded in dorsal view, propodeal spines slightly tending upwards and slender. Petiole with long peduncle and node convex on both sides, postpetiole with anterior concave side and posterior slightly convex side. Entire head, except clypeus and occipital margin, densely covered with longitudinal striae. Long and more marked striae are subparallel to each other. Between them, less marked striae can be found often crossing each other. Mesosoma mostly shiny, with horizontal striae appearing in proximity of sutures, across propodeum and posterior faces of petiole and postpetiole. Adpressed to decumbent setae on antennae, suberect to mostly erect setae on head, dorsal part of mesosoma, of petiole and postpetiole and all over gaster. Long setae extending down from clypeus. Adpressed to decumbent setae on legs.

Male
Male description (Figs 24, 25, 28, 33, 34). Measurements and indices (5 individuals, 1 locality): HL: 0.72 ± 0.02; HL: 0.72 ± 0.03; CI: 99.35 ± 1.44; FW: 0.48 ± 0.01; SL: 0.23 ± 0.01; SI: 32.65 ± 1.92; MW: 0.91 ± 0.09; ML: 1.73 ± 0.10. Whole body brown, appendages paler than rest of body. Head subtrapezoidal, occipital margin rounded, anterior margin of clypeus presenting small concavity, eyes large and oval. Antennae with thirteen segments, antennal club with five segments. Mesosoma elongated, with anterior gibbous part formed by prothorax, mesothorax and part of metathorax, and posterior part comparatively flat formed by part of metathorax and propodeum. Promesonotal suture well marked, pronotum and mesonotum convex in lateral view, rounded on side. Metathorax arched, consisting of subvertical and subhorizontal part. Subhorizontal part, in dorsal view, becomes very narrow in proximity of subvertical part. Propodeum not much thicker than horizontal part of metathorax in lateral view, bearing two particularly enlarged flat areas on its sides (better observed in dorsal view). Propodeal spines are absent and only represented by two tubercles. Petiole elongated, petiolar node and postpetiolar node rounded, both dorsally presenting shallow longitudinal suture in center. Scape very short, covered by rare decumbent setae, decumbent to subdecumbent setae also present on head, mesosoma and legs, a few erect setae on mesosoma, coxae, petiole and postpetiole, suberect to erect setae on gaster. Head finely reticulated, rest of body smooth and shiny.

Type Material
HOLOTYPE: 1 worker, Aphaenogaster trinacriae Alicata & Schifani, Italy – Sicilia – Custonaci TP. M. Sparagio, P.zzo Giacolamaro, 38°3’56.42”N 12°46’43.14”E 700 m, Alicata leg. – 2.III.1994, Quercus ilex forest – AACI-ANTP001/1, HOLOTYPUS des. Alicata & Schifani Aphaenogaster trinacriae det. Alicata & Schifani 2018. PARATYPES: IT ALY: SICILY: 2 ergatoids, same as holotype except AACI-ANTP001/3. PARATYPUS des. Alicata & Schifani (MSNG); 3 ergatoids, same as holotype except 22.XI.1996, AACI-ANTP002/2 PARATYPUS des. Alicata & Schifani (MSNG); 1 male, same as holotype except 8.VII.1997, from rearing – AACI-ANTP003/1 PARATYPUS des. Alicata & Schifani (in photo, MSNG); 1 male, same as holotype except 8.VII.1997, from rearing – AACI-ANTP003/2 PARATYPUS des. Alicata & Schifani (MSNG); 1 queen, same as holotype except AACI-ANTP001/2. PARATYPUS des. Alicata & Schifani (MSNG); 1 queen, same as holotype except 22.XI.1996, AACI-ANTP002/1, PARATYPUS des. Alicata & Schifani (MSNG); 4 ergatoids, Erice 10.xii.1993, leg. Alicata. PARATYPUS des. Alicata & Schifani, Aphaenogaster trinacriae det. Alicata & Schifani 2018 (MSNM); 8 ergatoids and 1 queen, Italy – Sicilia – Erice TP, M. Erice m 600, mixed forest, 10.XII.1993 leg. Alicata. PARATYPUS des. Alicata & Schifan Aphaenogaster trinacriae det. Alicata & Schifani 2018 (AACI); 2 ergatoids, Italy – Sicilia – Erice TP, M. Erice m 600, from rearing, 14.VII.1997 leg. Alicata. PARATYPUS des. Alicata & Schifani Aphaenogaster trinacriae det. Alicata & Schifani 2018 (AACI).

Etymology
Trinacria is the ancient Greek name of Sicily; noun in genitive case standing in apposition.

References based on Global Ant Biodiversity Informatics

 * Alicata A., and E. Schifani. 2019. Three endemic Aphaenogaster from the Siculo-Maltese archipelago and the Italian Peninsula: part of a hitherto unrecognized species group from the Maghreb? (Hymenoptera: Formicidae: Myrmicinae). Acta Entomologica Musei Nationalis Pragae 59: 1-16.
 * Scupola A., 2017. Aphaenogaster muelleriana Wolf, 1915 (Hymenoptera Formicidae) in Salento (South East Italy). Biodiversity Journal 8(1): 3-8.