Key to Stenamma westwoodii species-group workers of Western Europe and North African

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This worker key is based on: Rigato, F. 2011. Contributions to the taxonomy of West European and North African Stenamma of the westwoodii species-group. (Hymenoptera Formicidae). Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano. 37:1-56.

Workers are not known for Stenamma siculum and Stenamma msilanum

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Stenamma

1

  • Size usually larger (worker: TL ≥ 4.2, HL ≥ 0.94), dorsal face of scapes and extensor surface of meso- and metatibiae with few to several sparse, subdecumbent to suberect hairs in addition to the ordinary appressed to decumbent pubescence (Fig. 72) . . . . . 2
Rigato 2011. Fig. 72
  • Size usually smaller (worker: TL ≤ 4.3, HL ≤ 0.94), dorsal face of scapes and extensor surface of meso- and metatibiae with appressed to decumbent pubescence only (Fig. 71) . . . . . 3
Rigato 2011. Fig. 71

2

return to couplet #1

  • Size larger (TL around 5.0), body and appendages more slender (SI > 100, TI > 95), propodeum armed with relatively long and apically blunt spines which obliquely raise from the propodeal angles; postpetiole elongate, distinctly longer than high. (Fig. 25) (Italy) . . . . . Stenamma petiolatum
Rigato 2011 Stenamma petiolatum h.jpg
Rigato 2011 Stenamma petiolatum.jpg
Rigato 2011. Fig. 25
  • Size smaller (TL mostly around 4.5), body and appendages relatively shorter (SI < 100, TI around 90), propodeum simply toothed, when teeth are more developed they are somewhat upturned and nearly perpendicular to the propodeal dorsum; postpetiole stout, about as high as long. (Fig. 29) (N Italy, S Switzerland) . . . . . Stenamma zanoni
Stenamma zanoni casent0904561 h 1 high.jpg
Stenamma zanoni casent0904561 p 1 high.jpg
Rigato 2011. Fig. 29

3

return to couplet #1

  • Sculpture on head and promesonotum finer, more regularly longitudinally arranged with rare anastomoses (Fig. 34). Size small (TL < 3.5), propodeal spines usually longer (PSI > 1.50 to 2.00). (Widespread in S Europe and Turkey) . . . . . Stenamma striatulum
Stenamma striatulum casent0010683 head 1.jpg
Stenamma striatulum casent0010683 profile 1.jpg
Rigato 2011. Fig. 34
  • Sculpture on head and promesonotum coarser, with a less regular longitudinal pattern, head mostly areolate with many anastomoses (e.g. Fig. 33). Size larger (mostly TL ≥ 3.5), propodeal spines usually shorter (PSI often ≤ 1.50, and never approaching 2.00) . . . . . 4
Rigato 2011. Fig. 33

4

return to couplet #3

  • Promesonotal rugosity mostly longitudinally arranged, transverse only anteriorly just behind the neck (Fig. 31). Appendages shorter (nearly always SI ≤ 90 and TI < 85); scapes never reaching the posterior margin of the head when completely laid back. Petiolar sternite hardly concave in profile at the level of the node. Postpetiolar sternite straight in profile (Fig. 24). Colour usually darker, brown. (Widespread in Europe and Turkey) . . . . . Stenamma debile
Stenamma debile casent0010691 head 1.jpg
Stenamma debile casent0010691 profile 1.jpg
Rigato 2011. Fig. 31
Rigato 2011. Fig. 24
  • Promesonotal rugosity mostly irregular (e.g., Fig. 33), without a well defined longitudinal pattern, often forming a loose reticulum; if longitudinal rugulae prevail, they are strongly wandering. Appendages longer (nearly always SI ≥ 90 and TI > 85); scapes almost reaching, or even just reaching, the posterior margin of the head when completely laid back. Petiolar sternite weakly, but distinctly, concave in profile at the level of the node. Postpetiolar sternite in profile slightly, but distinctly concave (e.g., Fig. 26). Colour usually paler, ferrugineous . . . . . 5
Rigato 2011. Fig. 33
Rigato 2011. Fig. 26

5

return to couplet #4

  • Posterior portion of clypeus between frontal lobes at the level of antennal insertions distinctly narrower than each frontal lobe, about 1/5 to almost 1/4 of frontal lobes distance (PCI < 25). Promesonotal dorsum with a distinct longitudinal irregular median carina mostly crossed by transverse irregular rugulae (Fig. 35). Postpetiole appearing higher and stouter (Fig. 28). (UK, France, The Netherlands, Belgium) . . . . . Stenamma westwoodii
Rigato 2011 Stenamma westwoodii wh.jpg
Rigato 2011 Stenamma westwoodii wp2.jpg
Rigato 2011. Fig. 35
Rigato 2011. Fig. 28
  • Posterior portion of clypeus between frontal lobes at the level of antennal insertions about as wide as each frontal lobe, 1/4 to 1/3 of frontal lobes distance (nearly always PCI > 25). Promesonotal dorsum usually with an ill-defined or interrupted longitudinal median carina and irregularly widely reticulate rugose (Figs. 33, 37). Postpetiole lower and more slender (Figs. 26, 30) . . . . . 6
Rigato 2011. Fig. 33
Rigato 2011. Fig. 37
Rigato 2011. Fig. 26
Rigato 2011. Fig. 30

6

return to couplet #5

Stenamma africanum casent0913969 h 1 high.jpg
Stenamma africanum casent0913969 p 1 high.jpg
Stenamma sardoum casent0904150 h 1 high.jpg
Stenamma sardoum casent0904150 p 1 high.jpg