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Key to Lasius species of the subgenus Chthonolasius of Greece
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.
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1
- Whole surface of first gastral tergite with erected setae. Petiolar scale of variable shape . . . . . #2
- Dorsal area of first gastral tergite lacking erected setae except row of setae at front and posterior margin of the tergite. Petiolar scale very high with deeply excised upper margin . . . . . Lasius bicornis
A very distinct species, it differs from all congeners in central part of the first gastral tergite lacking erected setae, and narrow and high petiolar scale with extremely deep apical emargination.
2
return to couplet #1
- Erected setae on mesosomal dorsum long, GHL 0.058-0.135 mm. Dorsal surface of scape and external side of hind tibiae sometimes with setae . . . . . #3
- Erected setae on mesosomal dorsum very short, GHL 0.037-0.055 mm. Dorsal surface of scape and external side of hind tibiae without setae . . . . . Lasius mixtus
Within the subgenus, shortest setae on mesosomal dorsum and gastral tergites (GHL 0.037-0.055) and the longest setae on mesosoma < 0.064. It belongs to a species complex characterized by the dorsal surface of scape and external side of hind tibiae lacking erected setae and differs from Lasius citrinus and Lasius sabularum in absence of erected setae on scapus and hint tibiae, shallow emargination of apical margin of petiolar scale, and short erected setae on gaster.
3
return to couplet #2
- Petiole in caudal view slightly notched, concave, straight or convex dorsal crest and usually only slightly tapering dorsad . . . . . #4
- Petiole in caudal view with a deeply incised dorsal crest and strongly tapering dorsad. Genae usually with 0-3 setae . . . . . Lasius citrinus
Lasius citrinus differs from congeners in its subgenus by a very deeply emarginate petiolar scale and the scapus and hind tibiae lacking erect setae.
4
return to couplet #3
- Petiole not or slightly narrowing anterad, dorsal crest truncate or with shallow excavation at apex. Hind tibia without or with numerous erected setae . . . . . #5
- Petiole distinctly narrowing anterad, dorsal crest usually clearly convex or with very shallow notch at apex. Hind tibia with numerous erected setae . . . . . Lasius jensi
Lasius jensi differs from its Greek congeners by a narrow petiolar scale that narrows apically and has a bluntly pointed to narrowly rounded upper margin lacking apical emargination (sometimes upper margin with very small and shallow emargination). Also, it is one of the most setose members of the subgenus Chthonolasius with numerous erect setae on both anterior and posterior surfaces of scapus and external and lateral margins of hind tibia.
5
return to couplet #4
- Dorsum of first gastral tergite with dense to moderately dense pubescence and frontal face of the tergite with short setae. Surface of first gastral tergite more or less distinctly microsculptured, usually appears slightly dull or shiny . . . . . #6
- Dorsum of first gastral tergite with sparse pubescence and frontal face of the tergite with long setae. Surface of first gastral tergite with diffused microsculpture, appears smooth and shiny . . . . . Lasius nitidigaster
Differs from congeners by its smooth and shiny gaster with diffused microsculpture and very dilute pubescence, long and dense body hairs, and long scapus.
6
return to couplet #5
- Erected setae on mesosomal dorsum long, GHL > 0.090 mm. Dorsal surface of scape and external side of hind tibiae with several erected setae . . . . . #7
- Erected setae on mesosomal dorsum short, GHL< 0.090 mm. Dorsal surface of scape and external side of hind tibiae without setae or with only few semierected setae . . . . . Lasius sabularum
Short erected setae on mesosoma and usually lack of erect setae on antennal scapus and external margin of hind tibia place this species close to only Lasius mixtus. L.mixtus differs from L. sabularum in short and sparse setation of mesosoma (length of the longest seta <0.064) and short erected setae on gastral tergites.
7
return to couplet #6
- Small to moderate species, CW up to 1.044 mm. Second segment of antennal funicle moderately elongate, at most 1.5 times as long as wide. Pubescence of gaster moderately dense, the average distance between setae on first gastral tergite less than 35 μm. Hind tibia and antennal scape not to strongly flattened . . . . . #8
- Large species, CW up to 1.270 mm. Second segment of antennal funicle elongate, approximately 1.6 times as long as wide. Pubescence of gaster sparse, the average distance between setae on first gastral tergite is 35 μm. Hind tibia and antennal scape strongly flattened . . . . . Lasius viehmeyeri
Lasius viehmeyeri belongs to a complex of species with numerous erect setae on antennal scapus and the external margin of hind tibia. It differs from relatives in large body size with HW 1.270. Only the largest workers of Lasius citrinus have HW close to 1.250 but they differ in scapus and hind tibiae lacking erected setae.
8
return to couplet #7
- Hind tibia moderately wide and not strongly flattened, HTmax/CS distinctly less than 0.1449. Antennal scape moderately flattened. Appressed pubescence on gastral tergites denser . . . . . #9
- Hind tibia strongly widened and flattened, HTmax/CS up to 0.1449. Antennal scape strongly flattened. Appressed pubescence on gastral tergites sparser. Hind tibia with numerous standing setae . . . . . Lasius meridionalis
Lasius meridionalis belongs to a complex of species that have scapus and hind tibiae with suberect to erect setae. It differs from its relatives in a strongly widened and flattened hind tibiae with HTmax/CS up to 0.1449 and sparser appressed pubescence on its gastral tergites.
9
return to couplet #8
- External margin of hind tibia usually with less than 10 erected setae, sometimes lacking erected setae. Antennal scapus with only few semierected and erected setae, sometimes lacking erected setae. Here two species distinguishable only for characters of queen caste . . . . . Lasius balcanicus and Lasius distinguendus
Lasius balcanicus and Lasius distinguendus workers are part of a group with long erect mesosomal setae, a petiolar scale slightly broadened medially and slightly narrowed anterad with a shallowly emarginate upper margin, and antennal scapus and hind tibiae usually with few suberect to erect setae. These two ants are most similar, within their complex, to Lasius sabularum but it has distinctly shorter erect setae. Also, less setose specimens of Lasius umbratus can be confused with species of the balcanicus-distinguendus complex but they differ in antennal scapus and hind tibia always with erect setae (on external margin of hind tibia usually with more than 10 setae). Queens are needed to separate L. balcanicus from L. distinguendus as follows: L. balcanicus - Erect setae on anterior part of dorsal plane of first gastral tergite very long: GHL 0.137-0.176. Scape long SL/HW 0.804-0.962; L. distinguendus - Erect setae on anterior part of dorsal plane of first gastral tergite very long: GHL 0.080-0.092. Scape short SL/HW 0.732-0.787 . . . . .
- External margin of hind tibia usually with more than 10 erected setae. Antennal scapus with numerous semierect and erected setae . . . . . Lasius umbratus
Lasius umbratus belongs to a species complex characterized by a setose antennal scapus and external hind-tibia margin, and a petiolar scale that is slightly broadened medially, slightly narrowed anterad, and shallowly emarginate on the upper margin. L. umbratus is similar to the balcanicus-distinguendus complex but both species differ from L. umbratus in distinctly less setose antennal scapi and tibia. Small specimens of L. umbratus are similar to Lasius meridionalis but have distinctly narrower and unflattened hind tibiae.