Strumigenys species

Hamer, Matthew T. & Turner, Clive R., 2024, Strumigenys emmae (Emery, 1890) (Myrmicinae) new to Britain, with an updated key to the known Strumigenys of the West Palaearctic, Zootaxa 5415 (4), pp. 570-576 : 574-575

Taxonomic key of the native and introduced Strumigenys species known from Europe

This key is adapted from Hamer et al., (2021). An additional couplet (couplet 3) is provided here to enable identification of S. emmae within the European Strumigenys fauna. Italicised figure citations refer to figures within Hamer et al., (2021).

1 Mandibles narrow, MI 24–58, linear or bowed. At full closure mandibles engage only at their extreme apices and enclose an open space between them.Apicodorsal tooth of mandible long and spiniform, strongly crossing over the tooth from the opposite mandible when closed. Inner margin of mandible with 1–4 teeth or denticles (figure 6 A–D).......................... 2

- Mandibles triangular, MI 15–20. At full closure mandibles engage throughout their visible length, without an open space between them. Tooth at apex of mandible small and inconspicuous, not spiniform, not strongly crossing over the tooth from the opposite mandible when closed. Inner margin of mandible with 12–14 teeth and denticles, some of which may be minute (figure 6 E–H)............................................................................................. 5

2 Pronotal humeral hair absent. Dorsum of mesosoma without standing hairs (figure 7 A). Mandibles each with 3–4 preapical denticles. When mandibles fully closed the labral lobes are visible between them as a pair of elongate narrow triangles (figure 7 B). ( Austria, Azerbaijan, Bulgaria, Croatia, Czech Republic, France (southern mainland & Corsica), Georgia, Germany, Greece, Hungary, Israel, Italy (mainland, Sardinia & Sicily), Malta, Morocco, Russia (Caucasus), Serbia, Spain, Switzerland, Tunisia, Turkey)............................................................................... .. argiola (native)

- Pronotal humeral hair present (figure 7 C). Dorsum of mesosoma with at least one pair of standing hairs (figure 7 C & E). Mandibles each with 1–2 preapical teeth. When mandibles fully closed the labral lobes are not visible or at most appear between them as a pair of minute points basally (figure 7 D & F)....................................................... 3

3 Head dorsum covered in orbicular hairs ( figure 3 A ); antennae with four segments (including scape) ( figure 3 A ); scape short and expanded into convex lobe in median third of length ( figure 3 A ); leading edge of scape with orbicular hairs ( figure 3 A ); mandibles averaging shorter, MI 24-35 ( United Kingdom, Poland, The Netherlands).......... emmae (non-native[indoors])

- Head dorsum without orbicular hairs; antennae with six segments (including scape); scape long and linear, lacking convex median lobe; leading edge of scape without orbicular hairs; mandibles averaging longer, MI 34-57..................... 4

4 Ventrolateral margin of head interrupted by a deep, strongly incised preocular notch; in dorsal view anterior portion of eye is detached from side of head (figure 8 A & B). With head in ventral view the preocular notch forms the apex of a transverse impression in the ventral surface of the head capsule that extends toward the midline, well behind the postbuccal impression. First gastral sternite without a basal spongiform pad. Apicoscrobal hair absent. Pronotal humeral hair flagellate (figure 7 C). Mandibles each with 2 short preapical teeth, located close to the apicodorsal tooth, and the proximal preapical tooth longer than the distal (figure 6 B) ( United Kingdom, Germany, Denmark, Norway).................... rogeri (non-native[indoors])

- Ventrolateral margin of head uninterrupted to anterior margin of eye; in dorsal view anterior portion of eye is not detached from side of head (figure 8 C & D). With head in ventral view without a transverse impression in the ventral surface of the head capsule posterior to the postbuccal impression. First gastral sternite with a basal spongiform pad. Apicoscrobal hair present. Pronotal humeral hair straight and simple. Mandibles either with 1 spiniform preapical tooth, located close to the apicodorsal tooth, or also with a denticle close to the midlength which is much shorter than the spiniform preapical tooth (figure 6 C & D) ................................................................................................... 5

5 Leading edge of scape with all hairs curved toward the apex of the scape (figure 9 B). Ventral surface of petiole with a conspicuous strip or curtain of spongiform material (figure 9 A). Mandible with a single spiniform preapical tooth, located close to the apicodorsal tooth, without an additional denticle close to the midlength (figure 9 B). Dorsum of mesosoma obviously with more than one pair of standing hairs, on pronotum and mesonotum. Mandibles relatively slightly shorter, MI 34–48. ( Guernsey [British Channel Islands])...................................................... perplexa (non-native[outdoors])

- Leading edge of scape with 2 or more hairs curved toward the base of the scape (figure 9 D). Ventral surface of petiole entirely lacks spongiform material (figure 9 C). Mandible with a single spiniform preapical tooth, located close to the apicodorsal tooth, and also with an additional denticle close to the midlength (figure 9 D). Dorsum of mesosoma with only a single pair of standing hairs, on the mesonotum. Mandibles relatively slightly longer, MI 50–57 ( Portugal [Madeira], southern Atlantic Islands, Leiria district).................................................................... silvestrii (non-native[outdoors])

6 Humerus without a projecting hair; pronotum dorsolaterally with sharp raised margination (figure 10 A). Dorsal mesosoma and first gastral tergite without standing hairs (figure 10 A). Leading edge of scape with 1–2 hairs near the subbasal bend that are distinctly curved toward the scape base (figure 10 B). Dorsal surface of mandible basally with a very distinct transverse sharp edge or rim that extends across its width, parallel to and in front of the anterior clypeal margin (figure 10 B). CI 84–90, SI 51–57. ( France, Spain, Italy, Greece, Turkey, Norway).................. membranifera (non-native[outdoors & indoors])

- Humerus with a projecting simple hair; pronotum dorsolaterally without sharp raised margination (figure 10 C). Dorsal mesosoma and first gastral tergite with standing hairs (figure 10 C). Leading edge of scape with all hairs curved or inclined toward the scape apex (figure 10 D). Dorsal surface of mandible basally without a transverse sharp edge or rim running across its width (figure 10 D). CI 66–72, SI 69–76................................................................. 7

7 Dorsum of clypeus in full-face view densely clothed with conspicuous broadly spatulate to spoon-shaped hairs; in profile these hairs parallel with the surface from which they arise and closely applied (figure 11 A). Medially curved ground-pilosity bordering the upper scrobe margins distinctly spatulate. ( Algeria, Armenia, Bulgaria, Croatia, France (southern mainland & Corsica), Greece, Hungary, Italy (mainland, Sardinia & Sicily), Macedonia, Malta, Montenegro, Morocco, Romania, Russia, Serbia, Spain, Switzerland, Tunisia, Turkey)................................................... baudueri (native)

- Dorsum of clypeus in full-face view clothed with slender hairs that are very narrowly spatulate or simple and cylindrical; in profile these hairs markedly elevated and either arched or inclined anteriorly (figure 11 B). Medially curved ground-pilosity bordering the upper scrobe margins fine and simple.......................................................... 8

8 Hairs on clypeal dorsum narrowly spatulate; in profile the hairs distinctly anteriorly curved or anteriorly arched (figure 12 A). ( Bulgaria, France (mainland & Corsica), Greece, Italy, Spain, Turkey).............................. tenuipilis (native)

- Hairs on clypeal dorsum simple, fine and cylindrical throughout their length and tapered or truncated apically; in profile the hairs mostly straight, inclined anteriorly (figure 12 B). ( France ( Corsica), Greece)................... tenuissima (native)

Figures

FIGURE 3. Strumigenys emmae worker and queen specimens.A) S. emmae worker full face view, B) S. emmae worker lateral view, C) S. emmae worker dorsal view. D) S. emmae queen full face view, E) S. emmae queen lateral view, F) S. emmae queen dorsal view.