Key to Lasius species of the subgenus Lasius of Greece

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This key to workers is from Borowiec and Salata 2022. Each terminal couplet is followed by comparative remarks that are specific to the Greek ant fauna.

Due to the presence of many cryptic taxa, species of the subgenus Lasius s. str. are very difficult in identification. For correct identification, it is sometimes necessary to make a series of morphometric measurements, remove of allometric variance, and use statistical testing. The following identification key is therefore indicative only, and in doubtful cases, the reader should use the comments contained in Seifert’s (2020) paper.

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1

  • Pubescence on the whole body and appendages very smooth, appressed and short, all body surface completely smooth. Dorsal plane of scape, tibiae and genae lacking erected setae, number of mandibular dents only 6–8 . . . . . #2
  • Pubescence on the whole body and appendages moderate to dense, not very short, all body surface pubescent. Dorsal plane of scape, tibiae and genae with or lacking erected setae, number of mandibular dents usually above 8 . . . . . #3

2

return to couplet #1

  • Scape shorter, SL/HL < 0.890. Larger and stouter, HL 0.9312 ± 0.111, head from slightly wider than long to slightly longer than wide HL/HW 1.0353 ± 0.0292. Body often distinctly bicoloured with mesosoma lighter than head and gaster. First gastral tergite in central part without or with few erected setae . . . . . Lasius brunneus

Very smooth body with appressed and short pubescence on its whole surface place this species close only to Lasius lasioides. Morphological characters of both species largely overlap which may cause difficulties in their separation. However, L. brunneus is generally larger with stouter head (often wider than long in large workers) while in L. lasioides head is slimmer and always slightly longer than wide (also in large workers). L. brunneus is usually bicolored, especially large workers, with mesosoma lighter than head and gaster. While in L. lasioides head, mesosoma and gaster are usually the same color or mesosoma is only indistinctly paler than head and gaster. In L. brunneus first gastral tergite in central part is often lacking erected setae or have only few short setae while in L. lasioides surface of first gastral tergite is usually uniformly setose on the whole surface. In Greece, both species are partly separated ecologically, L. brunneus prefers shady mountain forests or, in northern Greece, wet and shady forests or trees close to water resources, streams and rivers. While L. lasioides prefers warm, luminous forest, seashores with Pinus trees and fryganas, also is common in parks and gardens inside tourist resorts and urban areas.

  • Scape longer, SL/HL > 0.890. Smaller and slimmer, HL 0.8411± 0.426, head always longer than wide HL/HW 1.0688 ± 0.0147. Body usually unicolor with mesosoma the same color as head and gaster. First gastral tergite in central part with several erected setae . . . . . Lasius lasioides

Very smooth body, with appressed and short pubescence covering the whole body and appendages, places this species close only to Lasius brunneus. Characters of both species largely overlap and cause difficulties in identifying. However, L. lasioides is generally smaller and has slimmer head (always slightly longer than wide, also in large workers). While L. brunneus is generally larger and has stouter head often wider than long in large workers. In L. lasioides head, mesosoma and gaster are usually of the same color or sometimes mesosoma is only indistinctly paler than head and gaster. While L. brunneus is usually bicolored, especially large workers, with mesosoma brighter than head and gaster. Also, In L. lasioides surface of first gastral tergite is usually uniformly setose on the whole surface while in L. brunneus the central part of first gastral is often lacking erected setae or have only few short setae. In Greece, both species are separated ecologically. L. lasioides prefers warm, luminous forests, seashores with Pinus trees and frygana, it is also common in parks and gardens inside tourist resorts and urban areas. While L. brunneus prefers shady mountain forests or in northern Greece, especially wet and shady forests or trees close to water resources, streams and rivers.

3

return to couplet #1

  • All workers in a nest very small, HL 0.66–0.75 mm, metanotal groove very shallow. Pubescence on head sides ventral of the eye reduced. Endemic to Crete . . . . . Lasius tapinomoides

A very distinct species. Very small body size and shallow metanotal groove is an unique combination of characters within Greek Lasius. Due to small number of mandibular teeth (7-8), only few erected setae on hind tibia, sparse clypeal pubescence, and shallow metanotal groove, L. tapinomoides appears to be a member of the L. turcicus complex. In Greece, occur three other species of this complex: Lasius turcicus, Lasius neglectus and Lasius precursor. None of these relatives have metanotal groove as shallow as in L. tapinomoides, all three are distinctly larger and none of them have erected setae on external surface of proximal part of hind tibia and suberected setae on antennal scape covering its 1/3 apical part.

4

return to couplet #3

  • Antennal scapi and hind tibiae with numerous erected setae . . . . . #5
  • Antennal scapi and hind tibiae lacking erected setae or only hind tibiae with few erected setae . . . . . #8

5

return to couplet #4

  • Pubescence of clypeus sparse, surface of the clypeus well visible. Erected setae on mesosoma relatively long. Body often bicoloured . . . . . #6
  • Pubescence of clypeus dense, covers a large part of the surface of the clypeus. Erected setae on mesosoma relatively short. Body always uniformly brown to black . . . . . Lasius niger

Lasius niger is a member of a complex of species with uniformly brown to black body and antennal scapi and tibiae with numerous erect setae. It differs from all relatives in pubescence of clypeus dense, covering a large part of the surface of the clypeus. Only Lasius platythorax is similar but it differs in clypeus with relatively sparse pubescence not covering the whole surface of the clypeus, and the longest erected setae on its scapus are longer than half of the maximum width of apical part of scape (in L. niger usually these setae are shorter). Also, both species differ in habitat preferences: L. niger prefers open and sunny habitats while L. platythorax is associated with deciduous, often shady forests. Dark forms of Lasius emarginatus and Lasius illyricus are also similar to L. niger but differ in sparse pubescence of clypeus.

6

return to couplet #5

  • Head and scape long (HL/HW 1.082-1.085, SL/CS 1.067-1.073). Body often bicolored but also uniformly brown to black. In Greece, widespread . . . . . #7
  • Head and scape short (HL/HW 1.051, SL/CS 0.981). Body always uniformly brown to black. In Greece, rare, only in northern provinces . . . . . Lasius platythorax

Lasius platythorax is a member of complex of species with uniformly brown to black body and antennal scapi and tibiae with numerous erect setae. Only Lasius niger is similar but it differs in pubescence of clypeus denser, covering a large part of the surface of the clypeus, and the longest erected setae on its scapus are usually shorter than half of maximum width of apical part of scape (in L. platythorax setae are longer). Also, both species differ in habitat preferences. Lasius platythorax is associated with deciduous, often shady forests while L. niger prefers open, sunny habitats. Dark forms of Lasius emarginatus and Lasius illyricus are also similar but differ in longer scapus with SL/HL usually above 1.0 (in L. platythorax usually below 0.97); L. illyricus differs also in strongly reduced erected setation on antennal scapi and distinctly less numerous erected setae on tibiae. Lasius platythorax is very rare in Greece known only from the northern part of the Macedonia province while both congeners are more widespread in Greek mainland and in Ionian Islands.

7

return to couplet #6

  • Scape in frontal view on dorsal apical 1/3 length has 2-3 erected setae, anterior surface of the scape in dorsal view with up to 4 erected setae ( occasionally up to 11 in large specimens) Setation on external edge of hind tibia sparser, with 6-18 erected setae (mean 13 ± 3) . . . . . Lasius illyricus (part)

Lasius illyricus belongs to the group of species with moderately numerous erected setae on antennal scapi and mid and hind tibiae. Morphotype 2 is similar to Lasius niger but differs in sparsely pubescent clypeus, head and mesosoma. Morphotype 1 is the most similar to Lasius emarginatus and Lasius platythorax. The latter species differs in slimmer head, shorter scapus, longer pronotal setae and lower propodeum. Both morphotypes of L. emarginatus differ from L. illyricus in distinctly higher number of erected setae on scapus, legs and metapleuron. In L. illyricus the scape in frontal view on dorsal apical 1/3 length has only suberect hairs and at most 3 erected setae, while in the same area in L. emarginatus erected setae predominate and their number is 6-11. The difference in chaetotaxy is more clearly visible on the anterior surface of the scape in dorsal view of antenna. In L. illyricus the surface has up to 4 erected setae (occasionally up to 11 setae in large specimens). While in L. emarginatus the number of long erected setae reaches usually 15-20 (up to 34) and only occasionally, in small specimens, the number can be lower (9-10 setae). L. illyricus has sparser setation on external edge of hind tibia with 6-18 erected setae (mean 13 ± 3), while in L. emarginatus this place has 13-27 erected setae (mean 20.8 ± 3.9). In L. illyricus the area below propodeal spiracle has usually up to two erected setae while in L. emarginatus the number of erected setae is 3-5. Greek specimens of L. illyricus, in comparison with Greek populations of L. emarginatus, are slightly larger (ML 1.352 ± 115.9 vs. 1.213.7 ± 94.7; HL 1.020 ± 72 vs. 1.002.3 ± 78.2, HW 0.981±99.5 vs. 0.952±97.6) and more distinctly bicolored with thorax usually distinctly paler from head and gaster.

  • Scape in frontal view on dorsal apical 1/3 length has more than three erected setae, anterior surface of the scape in dorsal view always with numerous erected setae, usually 15-20 (up to 34 in large specimens). Setation on external edge of hind tibia denser, with 13-27 erected setae (mean 20.8 ± 3.9) . . . . . Lasius emarginatus

Lasius emarginatus belongs to the group of species with rather numerous erected setae on antennal scapi, and mid and hind tibiae. Morphotype 2 is similar to Lasius niger but differs in sparsely pubescent clypeus, head and mesosoma. Morphotype 1 is the most similar to Lasius illyricus and Lasius platythorax. The latter species differs in slimmer head, shorter scapus, longer pronotal setae and lower propodeum. Lasius illyricus differs from L. emarginatus in distinctly lower number of erected setae on scapus, legs and metapleuron. In L. illyricus the scape in frontal view on dorsal apical 1/3 length has only suberect hairs and at most 3 erected setae, while in the same area in L. emarginatus erected setae predominate and their number is 6-11. The difference in chaetotaxy is more clearly visible on the anterior surface of the scape in dorsal view of antenna. In L. illyricus the surface has up to 4 erected setae (occasionally up to 11 setae in large specimens). While in L. emarginatus the number of long erected setae reaches usually 15-20 (up to 34) and only occasionally, in small specimens, the number can be lower (9-10 setae). Lasius illyricus has sparser setation on external edge of hind tibia with 6-18 erected setae (mean 13 ± 3), while in L. emarginatus this place has 13-27 erected setae (mean 20.8 ± 3.9).

8

return to couplet #4

9

return to couplet #8

  • Pubescence of clypeus dense, clypeal carina clearly developed. Body brown, mesosoma slightly lighter than head and gaster, reddish brown. Known only from Pindos Mts . . . . . Lasius karpinisi

Lasius karpinisi is difficult to identify as it lacks unambiguous identification characters. It is distinguished from other species with antennal scapi lacking erected setae and dense pubescence of clypeus by a combination of characters: elongate scape (Sl/HL 0.998-1.014), head broad with shallowly concave occipital margin, well developed clypeal carina and mesosoma reddish brown. Only Lasius illyricus have similar combination of characters but differs in antennal scapi with at least partly erect or semierect hair or setae and usually with more than 4 erected setae on hind tibiae.

  • Pubescence of clypeus sparse. Body bicolored or almost completely dark brown. Wide spread in continental Greece, Ionian islands and Crete . . . . . Lasius illyricus (part)

see couplet 7 for comparative remarks

10

return to couplet #8

  • Pubescence of clypeus dense, covers a large part of the surface of the clypeus . . . . . #11
  • Pubescence of clypeus sparse, surface of the clypeus well visible . . . . . #13


11

return to couplet #10

  • Species outside of Crete. Maxillary palps short to moderately elongate with length of sixth segment 0.102-0.176 . . . . . #12
  • Species endemic to Crete. Maxillary palps elongate with length of sixth segment 0.176-0.202 (mean 0.190) . . . . . Lasius kritikos

Lasius kritikos together with Lasius bombycina and Lasius paralienus form a complex of species characterized by antennal scapi lacking erected setae, hind tibiae with up to 4 erected setae in basal part, numerous erected setae in area below propodeal stigma, and especially by very dense pubescence of clypeus almost entirely covering its surface. Due to their morphological similarity their separation has to be supported with morphometric data. However, L. kritikos as an endemic of Crete and is separated geographically from both relatives. Lasius bombycina is the largest species of this complex and has the shortest maxillary palpi (length of sixth segment 0.102-0.151, mean 0.135) while L. kritikos is smaller but has the longest palpi (terminal segment with length 0.142-0.176, mean 0.160). L. paralienus has terminal segment of palpi shorter than in L. kritikos (length 0.142-0.176, mean 0. 160) and differs also in the shortest hair of mesosoma with length of the longest hair 0.075-0.134 (mean 0.134) vs. 0.116-0.147 (mean 0.134) in L. kritikos.

12

return to couplet #11

  • Terminal (6th) segment of maxillary palps longer (0.142-0.176, mean 0.160) and longest hair on pronotum shorter (length of the longest seta 0.075-0.134, mean 0.109). Very rare in Greece, only in north-western provinces . . . . . Lasius paralienus

Lasius paralienus together with Lasius bombycina and Lasius kritikos form a complex of species characterized by antennal scapi lacking erected setae, hind tibiae with up to 4 erected setae in basal part, numerous erected setae in area below propodeal stigma and especially by very dense pubescence of clypeus almost entirely covering its surface. Due to their morphological similarity their separation has to be supported with morphometric data. L. kritikos as a Cretan endemic and is separated geographically. L. paralienus is sympatric with L. bombycina in northern Greece but differs in longer terminal (6th) segment of maxillary palps (length 0.142-0.176, mean 0.160 vs 0.102-0.151, mean 0.135 in L. bombycina) and shorter hair on pronotum (length of the longest seta 0.075-0.134, mean 0.109 vs 0.108-0.185, mean 0.145 in L. bombycina).

  • Terminal (6th) segment of maxillary palps shorter (0.102-0.151, mean 0.151) and longest hair on pronotum longer (length of the longest setae 0.108-0.185, mean 0.145). Wide spread in Greece, except Crete, Cyclades and Dodecanese . . . . . Lasius bombycina

Lasius bombycina together with Lasius kritikos and Lasius paralienus form a complex of species characterized by antennal scapi lacking erected setae, hind tibiae with up to 4 erected setae in basal part, numerous erected setae in area below propodeal stigma, and especially by very dense pubescence of clypeus that mostly covers the clypeal surface. Identificaton of members of this complex is challenging and correct determinaton has to be supported with subtle biometric measurements. L. bombycina is the largest species of this complex and has the shortest maxillary palpi with length of sixth segment 0.102-0.151 (mean 0.135). While in both relatives the length of sixth segment always exceeds 0.140 and reaches up to 0.202. L. kritikos as an endemic of Crete is separated geographically while L. paralienus is sympatric with L. bombycina in northern Greece. L. paralienus differs from L. bombycina in longer terminal (6th) segment of maxillary palps with length 0.142-0.176, mean 0.160 (in L. bombycina 0.102-0.151, mean 0.151) and the longest hair on pronotum shorter (length of the longest seta 0.108-0.185, mean 0.145 vs 0.075-0.134, mean 0.109 in L. paralienus).

13

return to couplet #10

  • Area between propodeal spiracle and metapleural gland with 2-6 erected setae. Occipital margin of head usually with more than 15 erected setae . . . . . #14
  • Area between propodeal spiracle and metapleural gland lacking erected setae or at most with a single seta. Occipital margin of head with less than 15 (usually 8-12) standing setae. Pronotal setae rather long PnHL/CS 0.152 ± 0.007. Clypeal pubescence moderately dense. Propodeum high and angular in profile . . . . . Lasius alienus

Lasius alienus differs from all similar Greek species in reduced pilosity of scape and tibiae, strongly reduced number of erected setae below propodeal spiracle and less numerous setae on occipital part of head. Its specimens with 2-4 erected setae on hind tibia are similar to Lasius psammophilus or Lasius creticus but differs in denser clypeal pubescence and less numerous erected setae on occipital part of head.

14

return to couplet #13

  • Mean number of mandibular dents > 8. External margin of hind tibiae usually with 1-4 erected setae. Pubescence distance on clypeus moderately large. Propodeum high . . . . . #15

The Lasius turcicus complex is characterized by: antennal scapi lacking erected setae, hind tibiae with at most a single erected seta basally, numerous erected setae in area below propodeal stigma, and short and sparse pubescence of clypeus. Also, this complex is well distinguished from other species by the lowest number of denticles (6-7) on masticatory border of mandibles, hind tibiae usually lacking erected setae and rather low and obtuse propodeum.

15

return to couplet #14

  • Short setae on hind margin of head and gula (GuHL/CS900 0.097). Continental Greece, dominant ant species on mountain pastures at altitude between 1000 to 1720m . . . . . Lasius psammophilus

Lasius psammophilus with Lasius creticus form a complex of species characterized by antennal scapi lacking erected setae, hind tibiae with up to 4 erected setae in basal part, numerous erected setae in area below propodeal stigma and especially by short and sparse pubescence of clypeus not covering the clypeus surface. Identificaton of members of this complex is challenging and correct determinaton has to be supported with subtle biometric measurements. L. psammophilus is known only from Greek mainland while L. creticus is distributed in southern islands from Crete to Dodecanese. Also, L. creticus has longer maxillary palpi (length of terminal segment 0.166-0.181 and mean 0.171 vs. 0.0.091-0.134 and mean 0.117 in L. psammophilus). Lasius creticus differs also in slightly longer hair of mesosoma (length of the longest hair 0.110-0.147 and mean 0.124 vs. 0.091-0.143 and mean 0.114 in L. psammophilus).

  • Long setae on hind margin of head and gula (GuHL/CS900 0.125). Crete and Dodecanese, thermophilous species of low and mid habitats from sea level to 1000 m . . . . . Lasius creticus

Lasius creticus with Lasius psammophilus form a complex of species characterized by antennal scapi lacking erected setae, hind tibiae with up to 4 erected setae in basal part, numerous erected setae in area below propodeal stigma, and especially by short and sparse pubescence of clypeus that do not cover entirely the clypeal surface. Identificaton of members of this complex is challenging and correct determinaton has to be supported with subtle biometric measurements. L. creticus is distributed in southern islands, from Crete to Dodecanese, while L. psammophilus is known only from Greek mainland. Also, L. creticus has longer maxillary palpi with length of terminal segment 0.166-0.181 (mean 0.171) vs. 0.0.091-0.134 (mean 0.117) in L. psammophilus. L. creticus differs also in slightly longer hair of mesosoma with length of the longest hair 0.110-0.147 (mean 0.124) vs. 0.091-0.143 (mean 0.114) in L. psammophilus.

References

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