Key to males of the Linepithema fuscum group

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This key to identify the males of known species of the Linepithema fuscum group is based on Cantone & Di Giulio (2023).

The form of the volsella in the species of Linepithema fuscum group is the main morphological feature used by Wild (2007) to differentiate the species. The digitus was divided by Wild (2007) into proximal arm and distal arm (Fig. 7D). We follow this criterion, which gives the possibility to compare species of the fuscum group (Fig. 7).

  • Cantone & Di Giulio (2023), Figure 7. Shape of volsella in males of the Linepithema fuscum-group: A, L. paulistana; B, L. angulatum; C. L. piliferum; D. L. fuscum; E, L. keiteli; F, L. tsachila. Abbreviations: dp = proximal arm of digitus; dd = distal arm of digitus. B–F re-drawn from Wild (2007).

1

  • Forewings with one submarginal cell; petiole with ventral process well developed (Fig. 5A, B); pygostyle short (Fig. 5C); proctiger slightly developed (Fig. 5E, F); telomere short and lobiform (Fig. 5C, D); lateral cuspis developed (Fig. 5E, F); ventral basivolsellar process developed (Fig. 5E, F) => Linepithema species not in the fuscum group
  • Cantone & Di Giulio (2023), Figure 5. L. humile: A, petiole in lateral view; C, external genitalia in lateral view; E, external genitalia in posterior view; G, valviceps lamina. L. neotropicum: B, petiole in lateral view; D, external genitalia in lateral view; F, external genitalia in posterior view; H, valviceps lamina. Abbreviations: ba: basimere; bvp: basivolsellar process; cu: cuspis; dg: digitus; mgo: metapleural gland orifice; ps: petiole spiracle; prs: propodeal spiracle; pl: ventral petiolar process; pm: penisvalve membrane; te: telomere; vc: valviceps lamina.
  • Forewings with two submarginal cells (Fig. 1E); petiole with ventral process slightly developed consisting of a slight convexity (Figs 1D, 3D); pygostyle very long (Fig. 4A); proctiger well developed (Fig. 1G, I); telomere very long and narrow (Fig. 4C); lateral cuspis very reduced (Fig. 4E); ventral basivolsellar process reduced (Fig. 4D) => 2 (Linepithema fuscum group)
  • Cantone & Di Giulio (2023), Figure 1. L. paulistana: A, habitus; B, head in dorsal view; C, head in lateral view; D, petiole in lateral view; E, forewing; F, hindwing; G, external genitalia in lateral view; H, abdominal sternite IX; I, tergite IX+proctiger; J, valviceps lamina. Abbreviations: A: anal vein; atIX: abdominal tergite IX; asIX: abdominal sternite IX; BA: basal cell; CS: costal cell; Cu: cubital vein; cu-a: cubito-anal crossvein; DSC: discoidal cell; MA: marginal cell; M+Cu: medio-cubital vein; plc: petiole ventral postero-lateral carina; pg: pygostyle; pr: proctiger; Rs1: radial sector 1 vein; Rs2: radial sector 2 vein; rs-m+M1: radial sector-media crossvein; rs-m: radial sector-media cross-vein; 2r-rs: 2 radius-radial sector crossvein; R1: Radius 1; Rs1: Radial sector 1; Rs2: Radial sector 2; SBA: subbasal cell; SM1: submarginal 1 cell; SM2: submarginal cell 2; te: telomere; vc: valviceps; vo: volsella; vt: volsellar tooth.
  • Cantone & Di Giulio (2023), Figure 3. L. paulistana: A, mesosoma dorsal view; B, mesosoma ventral view; C, mesosoma dorsal view; D, tegula; E, petiole; F, protibial spur and mesotibial spur; G, metatibial spur. Abbreviations: ane: anepisternum; asII: abdominal sternum II; ax: axilla; cms: medial coxal articular process of the mesopectus; cmt: medial coxal articular process of the metapectus; lmt: lower metapleuron; kat: katespisternum; mca: medial coxal articular process of the metapectus; md: mesodiscrimen; mef: mesocoxal foramen; mf: metacoxal foramen; mes: mesoscutum; msc: mesoscutellum; met: metascutellum; mgo: metapleural gland orifice; msa: mesoscutellar arm; mse: mesepimeron; msf: mesoprefurcal pit; mtf: metaprefurcal pit; msp: mesopleural pit; mss: mesopleural suture; mta: metascutellar arm; mtl: metascutellar line; mtp: metatentorial pit; mts: metapleuropropodeal suture; mtt: metascutellar trough; pal: parapsidal line; plc: petiole ventral posterolateral carina; pro: pronotum; prp: propodeum; prs: propodeal spiracle; ps: petiole spiracle; px: preaxilla; sa: subalar area; ss: scutoscutellar sulcus; ssc: spiracular sclerite; ssu: scutoscutellar suture; trl: transscutal line; tg: tegula; umt: upper metapleuron.
  • Cantone & Di Giulio (2023), Figure 4. L. paulistana: A, external genitalia lateral view; B, external genitalia ventral view; C, external genitalia ventro-lateral view; D, volsella and valviceps lateral view; E, basimere and volsella in lateral view; F, basimere and volsella in medial view. Abbreviations: asIX: abdominal sternite IX; atVIII: abdominal tergite VIII; pr: proctiger; ba: basimere; bvp: basivolsellar process; cu: cuspis; dg: digitus; pg: pygostyle; pm: penisvalve membrane; te: telomere; tem: telomere membrane; vc: valviceps; vo: volsella; vt: volsellar tooth.

2

  • Digitus very long, downturned, falcate (Fig. 7A, B, D, E) => 3
  • Digitus moderately long, not downturned, not falcate (Fig. 7C, F) => 6
  • Cantone & Di Giulio (2023), Figure 7. Shape of volsella in males of the Linepithema fuscum-group: A, L. paulistana; B, L. angulatum; C. L. piliferum; D. L. fuscum; E, L. keiteli; F, L. tsachila. Abbreviations: dp = proximal arm of digitus; dd = distal arm of digitus. B–F re-drawn from Wild (2007).

3

  • Basivolsellar process not pointed apically (Fig. 7B) => Linepithema angulatum
  • Basivolsellar process pointed apically (Fig. 7A, D, E) => 4

4

  • Digitus downturned with almost a 90° angle (Fig. 7E); ocular index OI = 37–42; Hispaniola island => Linepithema keiteli
  • Digitus downturned with 45° angle (Fig. 7A, D); ocular index OI = 47–52 => 5

5

  • Volsellar tooth present distally between basivolsellar process and digitus (Fig. 7A); São Paulo, Brazil => Linepithema paulistana
  • Volsellar tooth absent (Fig. 7D); Peru and Ecuador => Linepithema fuscum

6

References

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