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

This worker key is based on: [[Media:Rigato 2011.pdf| 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. PDF]]

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


 * 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

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


 * 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

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


 * 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

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


 * 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

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


 * 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

6
return to couplet #5
 * SI ≥ 95. (Tunisia and Algeria) . . . . . Stenamma africanum


 * SI ≤ 96. (Italy: Sardinia) . . . . . Stenamma sardoum