A new species of the ant genus Lasius Fabricius, 1804 from Crete (Hymenoptera, Formicidae)

Abstract Lasiustapinomoidessp. n. from Crete, Greece, is described and illustrated. It belongs to L.turcicus complex and is well characterized by very small body, extremely shallow metanotal groove and presence of suberect to erect setae on the apical part of scape. New records of Cretan members of the genus Lasius Fabricius, 1804 are provided, their checklist is updated, and the key to their determination is presented.


Introduction
The genus Lasius Fabricius, 1804 is widely distributed throughout the Holarctic. Within its range, it is one of the most abundant of all Formicidae genera and its species are very often dominants of local myrmecofauna (Janda et al. 2004). Forty-three Lasius species are known from Europe and Mediterranean area (Borowiec 2014, Talavera et al. 2015, Seifert and Galkowski 2016, divided in five subgenera (Maruyama et al. 2008). The most numerous is the nominotypical subgenus Lasius s. str. Ruzsky, 1913 -23 spe-Specimens of Lasius tapinomoides sp. n. were compared with all other known Cretan species of the genus Lasius and type material of members of the Lasius alienus group listed below. Type specimens photographs of the Lasius alienus group members are available online on AntWeb (www.AntWeb.org) and are accessible using the unique CASENT or FOCOL identifying specimen code. Moreover, we compared them with samples of members of the Lasius alienus group from other Greek regions. Data concerning distribution of Greek Lasius samples used in the comparison is provided in series of regional checklists (Borowiec and Salata 2012, 2013, 2014, 2017a,b, 2018, Bračko et al. 2016. Therefore, we see no reason to repeat this information. The list of Cretan Lasius species, together with their occurrence data on the island is provided below. This study was also supported by data published in recent revisions of Lasius s. str. (Seifert 1992, Talavera et al. 2015, Seifert and Galkowski 2016. We decided to list all other ant species collected from the same localities where the new species has been found. In our opinion it provides valuable information about ecosystem structure and species diversity characteristic for habitats preferred by this species. Distribution maps of all recorded Lasius species were created in DivaGis 7.5 (Hijmans et al. 2011 35°15.245 N,24°34.220, 342m, 11.v.2013, leg. S. Salata (DBET); 5w. (EtOH), road to Preveli Beach loc. 1, 35. 16666N,24.45E, 58m, 7.v.2013, leg. S. Salata (DBET).
Etymology. The name refers to the similarity of this species to species of the Tapinoma genus, caused by a very shallow metanotal groove.
Description. Worker. Measurements: see Table 1. Head, mesosoma, petiole and gaster uniformly coloured, brown to dark brown. Antennae, tibiae and tarsi bright brown to orange (Figs 1-4). Head oval, 1.2 times as wide as long, lateral surfaces above eyes convex, occipital margin of head slightly convex (Figs 3-4). Clypeus shiny and smooth, its anterior margin convex, lacking median anterior notch, covered with sparse, decumbent to erect pubescence, average distance between setae longer than three fourths of their length. Masticatory border of mandibles with 7-8 teeth. Eyes medium-sized, oval, 0.25 times as long as length of the head. Antennal scape long, straight or slightly curved on its anterior part, 0.9 times as long as length of the head, exceeding beyond occipital margin of head, in apex gradually widened. Pedicel more than 2.0 times longer than wide, average 2.5 times longer than second segment of funiculus. Other funicular segments from 1.5 to 2.0 times longer than wide (Figs 3-4). Surface of scape with very fine microreticulation, shiny. Its surface covered with thin, dense, adpressed setae, on its apical part several suberect setae also occur.
Genae with few adpressed to suberect setae ( Figure 3). Underside of head with thin, dense, adpressed setae and a few long, suberect to erect setae ( Figure 1). Whole frontal head surface covered with short, adpressed and dense pubescence and sparse, long, thick suberect to erect setae, the distance between setae at least as long as three fourths of their length (Figs 3-4). Mesosoma short, 1.9 times as long as wide. In lateral view, promesonotum low and flattened, metanotal groove very shallow, propodeum very low, propodeal dorsum slightly convex, propodeal declivity convex, less than twice length of propodeal dorsum ( Figure 1). Whole mesosoma surface shiny with sparse microreticulation, covered with short, adpressed and dense pubescence, and sparse, long, thick suberect to erect setae, the distance between setae at least as long as half of their length, metapleuron below the level of the propodeal spiracle with more than 5 setae (Figs 1-2). Petiole scale low, in lateral view with slightly convex sides, its dorsal crest thick and arched ( Figure 1). Gaster with very rare and fine microreticulation, shiny, bearing pilosity similar to this covering mesosoma. Legs long, shiny, with fine microreticulation. Surface of tibia and femora with thin, dense, adpressed to subdecumbent setae, extensor profile without erect setae (Figs 1-2 Head, mesosoma, petiole and gaster dark brown. Antennae, tibiae and tarsi bright brown to orange (Figs 5-7).
Head trapezoidal, 1.1 times as wide as long, lateral surfaces above eyes convex, sides of occipital margin of head slightly convex, its central part concave ( Figure 5). Clypeus shiny and smooth, its anterior margin convex, lacking median anterior notch, covered with decumbent to erect setae, average distance between setae longer than one third of their length. Masticatory border of mandibles with seven teeth. Eyes mediumsized, oval, 0.3 times as long as length of the head. Antennal scape short, curved on its anterior part, 0.9 times as long as length of the head, slightly exceeding beyond occipital margin of head, in apex gradually widened. Pedicel more than 2.0 times longer than wide, 2.0 times longer than second segment of funiculus. Other funicular segments from 1.5 to 2.0 times longer than wide ( Figure 5). Surface of scape with very fine microreticulation, shiny. Its surface covered with thin, dense, adpressed to decumbent pubescence, on its apical part a few short, suberect setae also occur. Genae with thin, dense adpressed pubescence and a few suberect setae ( Figure 5). Underside of head with thin, dense, adpressed pubescence and a few long, suberect setae ( Figure 6). Whole frontal head surface covered with short, adpressed and dense pubescence and sparse, long, thick suberect to erect setae, the distance between setae at least as long as three fourths of their length (Figs 5-6).
Mesosoma long, 1.6 times as long as wide. In lateral view moderately high, its dorsum slightly convex, propodeal dorsum slightly convex, propodeal declivity convex ( Figure 6). Whole mesosoma surface shiny with very sparse microreticulation, covered with short, adpressed and dense pubescence, and sparse, long, thick suberect to erect setae, the distance between setae at least as long as half of their length (Figs 6-7).
Petiole scale low and wide, in lateral view with slightly convex sides, its dorsal crest wide and deeply concave in central part. Gaster with moderately thick and fine microreticulation, shiny, bearing pilosity denser than this covering mesosoma. Legs long, shiny, with fine microreticulation. Surface of tibia and femora with thin, dense, adpressed to subdecumbent setae, extensor profile of tibia with erect setae (Figs 6-7). Differential diagnosis. Worker. As a member of the L. alienus group it is characterized by dorsal plane of scape, genae, and extensor profile of hind tibiae lacking or having very few erect or suberect setae and, in all species known from Crete, presence of >15 erect setae on the occipital edge of the head. Within the L. alienus group it can be classified to the L. turcicus complex. This complex can be characterized by small number of mandibular teeth (6-8), usually lack of suberect setae on hind tibia, very sparse clypeal pubescence, and more or less shallow metanotal groove. There are three known species of this complex: L. turcicus, L. neglectus and L. austriacus. Lasius tapinomoides sp. n. differs from all of them in presence of suberect to erect setae on antennal scape covering its apical part (ca. 1/3 upper part of the scape). Additionally from first two relatives it differs also in very shallow metanotal groove and from L. austriacus it differs in more flattened promesonotum, antennal sockets set not very close to posterior clypeal margin and habitat preferences. Lasius austriacus is related with xerothermous sites (Schlick-Steiner et al. 2003, Steiner et al. 2004) while L. tapinomoides inhabits moist, closed canopy forests.
There are two other species of the L. alienus group known from Crete: L. bombycina Seifert &Galkowski, 2016 andL. turcicus Santschi, 1921 Gyne. During our fieldwork we could observe several gynes of L. tapinomoides and all detected nests were monogynous. Unfortunately, we were able to collect only a single specimen, therefore we provide very scarce data. As a coherent differential diagnosis is impeded, we decided to limit it to the most visible difference. Based on the morphology, L. tapinomoides differs from L. turcicus, L. austriacus and L. neglectus in presence of erect setae on tibiae.
General distribution. Greece: Crete -endemic species. Biology. Species inhabiting moist, closed canopy forests, which are most often located in stream valleys. Nesting in wet soil, under shallow and small rocks. Nests, most often, located in the vicinity of water sources. Workers were found in the litter or on the rocks surrounding the nest entrance. Colonies monogynous.