Strumigenys Smith, 1860

Tang, Kit Lam & Guénard, Benoit, 2023, Further additions to the knowledge of Strumigenys (Formicidae: Myrmicinae) within South East Asia, with the descriptions of 20 new species, European Journal of Taxonomy 907, pp. 1-144 : 132-136

Key to Strumigenys Smith, 1860 of East Asia

(as Pyramica Roger, 1862 ) [partial, updated]

The following key is a partial overhaul of the original key to Strumigenys of East Asia (as Pyramica ) by Bolton (2000), replacing couplets 37–56. New species described since the publication of the original key, which would be keyed out around the above couplets, are included. This includes all known East Asian species from the S. acubecca -, S. bubisnoda -, S. leptothrix -, S. nathistorisoc -, S. semicompta - and S. wilsoniana -groups. Some of the couplets are only slightly modified from the original. As more than two dozen of species are added, the original couplet numberings are not retained.

1. (Couplet 37 of the original key) Mandibles elongate and narrow in full-face view; masticatory margins engage only in apical half or less of their length at full closure, proximally with large gap between mandibles; labral lobes visible through gap; MI>25 ......................................................... 2

– Mandibles triangular to elongated-triangular in full-face view; masticatory margins engage throughout their length at full closure, proximally without large gap between mandibles; labral lobes not visible; MI<25 ............................................................................................................................ 4

2. When fully-closed, mandibles entirely dentate from base to apex in full-face view; teeth range from triangular, spiniform to broad and rounded (Mainland China) ........................................................................... Strumigenys nathistorisoc Tang et al., 2019

– When fully-closed, mandibles edentate from base to about the mid-length in full-face view; teeth triangular and spiniform, without broad and rounded tooth ............................................................. 3

3. Flagellate setae present on dorsolateral margins of head, pronotal humeri, petiole, postpetiole, first gastral tergite and dorsal (outer) surfaces of tibiae and basitarsi. Aligned rows of appressed spatulate setae entirely absent. Anterior clypeal margin with small median tooth. Eye minute, with only 3–4 ommatidia in total. Scape long and slender, SI>100. ( Malaysia (Peninsular)) .......................................................................... Strumigenys acubecca (Brown, 1972)

– Flagellate setae entirely absent. Aligned rows of appressed spatulate setae conspicuous on cephalic dorsum, scapes and mandibles. Anterior clypeal margin evenly convex. Eye relatively large, with 5 ommatidia in longest row. Scape short and stout, SI <70. (Mainland China) ........................................................................ Strumigenys wilsoniana Baroni Urbani, 2007

4. Masticatory margin of mandible with total dental count of 5; all stoutly conical and slightly recurved teeth, without denticles. Anterior clypeal margin transverse or nearly so. Apices of labral lobes truncated ........................................................................................................................................... 5

– Masticatory margin of mandible with total dental count of 12–18; with basal series of 6–9 teeth that may be elongated-triangular, broad and rounded, conical or spiniform; distal to this series number of smaller teeth and denticles.Anterior clypeal margin convex. Apices of labral lobes may be triangular, conical or digitate, but never truncated ............................................................................................. 7

5. Dorsal (outer) surfaces of middle and hind tibiae and basitarsi with numerous erect long simple setae. Dorsal surfaces of middle and hind femora with suberect to erect elongate simple setae. Leading edge of scape with row of short suberect clavate setae. Basigastral costulae extend for some distance onto sclerite proper, not restricted to limbus. ( Indonesia ( Maluku Islands), Papua New Guinea, also present in Australia) ........................................................... Strumigenys semicompta (Brown, 1959)

– Dorsal (outer) surfaces of middle and hind tibiae and basitarsi with short decumbent to appressed setae. Dorsal surfaces of middle and hind femora without elongate simple setae. Leading edge of scape with row of closely appressed minute setae. Basigastral costulae extremely short, traversing limbus but barely extending onto sclerite proper ............................................................................. 6

6. Cephalic dorsum behind clypeus entirely sculptured, with longitudinal rugulae present. Dorsolateral margin of occipital lobe with 3 short stiff projecting setae; dorsum of head with a few erect short setae near occipital margin. Pronotal humeral seta present, stiff and projecting laterally. Dorsal mesosoma with short erect setae present along dorsolateral margins. ( Papua New Guinea) ................................................................................... Strumigenys carnassa ( Bolton, 2000)

– Cephalic dorsum behind clypeus mostly smooth, without longitudinal rugulae. Dorsolateral margin of occipital lobe without projecting setae; dorsum of head without erect setae. Pronotal humeral seta absent. Dorsal mesosoma without erect setae anywhere. ( Indonesia (New Guinea)) ........................ .................................................................................................... Strumigenys pydrax ( Bolton, 2000)

7. Postpetiole enormously inflated, PPL 0.42. Larger species, HL 1.22. Head in profile extremely dorsoventrally flattened, its depth at level of eye only slightly greater than maximum diameter of eye. Propodeal spiracle located at apex of V-shaped depression inside sclerite. ( Malaysia (East Malaysia)) ............................................................................ Strumigenys bubisnoda ( Bolton, 2000)

– Postpetiole small, PPL<0.3. Smaller species, HL<0.90. Head in profile not dorsoventrally flattened, its depth at level of eye much greater than maximum diameter of eye. Propodeal spiracle not located at apex of a V-shaped depression inside sclerite ............................................................................... 8

8. In profile view, propodeal declivity with simple carina, or at most narrow lamella with posterior margin close to and parallel with edge of declivity .......................................................................... 9

– In profile view, propodeal declivity with broad lamella, posterior margin not close to nor parallel with edge of declivity ..................................................................................................................... 17

9. Dorsal (outer) surface of hind tibia without suberect to erect projecting setae; any setae present are decumbent to appressed .................................................................................................................. 10

– Dorsal (outer) surface of hind tibia with suberect to erect projecting setae ................................... 14

10. Propodeal lobes (at base of declivity) elongate, narrowly acutely triangular. Declivity above propodeal lobe margined only by vestigial carina extending upward to propodeal spine ...............11

– Propodeal lobes (at base of declivity) short, low and rounded. Declivity above propodeal lobe margined by narrow lamella distinctly engaging base of propodeal tooth or spine ....................... 13

11. With head in profile view, dorsal outline of clypeus forming shallow even convexity with highest point at about mid-length; clypeal outline sloping evenly and gently upward from basal margin of mandible to highest point and posterior to this sloping evenly and gently downward to posterior clypeal apex .................................................................................................................................... 12

– With head in profile view, dorsal outline of clypeus not forming even shallow convexity with highest point at about mid-length; clypeal outline rising almost vertically from basal margin of mandible and passing through bluntly bulging angle (vertical portion accounts for about onethird of length of outline), posterior to this outline almost flat to posterior clypeal apex. (East Malaysia) ................................................................................ Strumigenys megaera ( Bolton, 2000)

12. With head in profile view, dorsum with single transverse row of 4–6 short standing setae posteriorly, immediately in front of occipital margin. In full-face view dorsolateral margin of occipital lobe without freely projecting stiff setae. Head narrower and scape longer, CI 56–60, SI 81–86. ( Thailand) ............................................................................... Strumigenys scolopax ( Bolton, 2000)

– With head in profile view, dorsum with numerous standing setae posteriorly, obviously more than single row immediately in front of occipital margin. In full-face view dorsolateral margin of occipital lobe with 4–5 freely projecting stiff setae. Head broader and scape shorter, CI 65–70, SI 71–77. ( Malaysia (Peninsular), Indonesia (Java )) .............................. Strumigenys rudinodis Stärcke, 1941

13. Side of pronotum, mesopleuron, metapleuron and side of propodeum entirely smooth and shining; pronotum strongly marginated dorsolaterally ( Vietnam) ......................... Strumigenys rongi sp. nov.

– Side of pronotum and propodeum entirely sculptured, mesopleuron and metapleuron only partly smooth and shining; pronotum at most weakly marginated dorsolaterally (Mainland China, Korea, Japan, Taiwan) ................................................................................. Strumigenys japonica Ito, 1914

14. With head in full-face view, upper scrobe margin with continuous row of short anteriorly directed decumbent to appressed setae only, without elongate setae freely projecting beyond margins; one or two freely projecting setae may occur on lateral occipital lobes well behind level of eyes. ( Malaysia (East Malaysia), Philippines) .................................................... Strumigenys euryale ( Bolton, 2000)

– With head in full-face view, upper scrobe margins with straight or curved elongate setae freely projecting laterally or dorsolaterally beyond margins; similar or even longer setae project from occipital lobes ................................................................................................................................. 15

15. Leading edge of antennal scape with series of straight anteriorly projecting setae; dorsum of petiolar node unsculptured ( Indonesia (Sulawesi )) ................................. Strumigenys stheno ( Bolton, 2000)

– Leading edge of antennal scape without series of straight anteriorly projecting setae; dorsum of petiolar node fully sculptured ......................................................................................................... 16

16. Propodeal lobes elongate and narrowly triangular, more than half length of propodeal spines. Elongate setae on dorsum of head erect in profile view, weakly curved or sinuate along their length but not strongly arched forward. Pronotal dorsum with spaces between longitudinal costulae vestigially punctulate to smooth. ( Malaysia (East Malaysia)) ................... Strumigenys medusa ( Bolton, 2000)

– Propodeal lobes short and broadly triangular, much less than half length of propodeal spines. Elongate setae on dorsum of head strongly arching forward in profile view, their apices directed anteriorly. Pronotal dorsum with spaces between the longitudinal costulae densely reticulate-punctate. ( Papua New Guinea, Philippines) ............................................................ Strumigenys scylla ( Bolton, 2000)

17. Dorsal (outer) surface of hind tibia without suberect to erect projecting setae; any setae present are decumbent to appressed .................................................................................................................. 18

– Dorsal (outer) surface of hind tibia with suberect to erect projecting setae ................................... 23

18. Dorsal mesosoma entirely lacking standing setae .......................................................................... 19

– Dorsal mesosoma with standing setae present at least on the mesonotum ..................................... 20

19. With petiole in profile view, lateral spongiform lobe very broad and extending forward to level of spiracle on peduncle. Propodeal spines or teeth absent. (Mainland China, India, Vietnam) ....................................................................... Strumigenys assamensis De Andrade, 1994

– Withpetioleinprofileview,lateralspongiformlobenotextendingforwardtolevelofspiracleonpeduncle. Propodeum with pair of spines or acute teeth. (Mainland China) ....... Strumigenys zanderi sp. nov.

20. With head in full-face view, dorsolateral margin of head strongly marginated; lateral margin of occipital lobe and upper scrobe margin forming blunt angle. Pronotum marginated dorsolaterally. ( Thailand) ...................................................................................... Strumigenys decumbens sp. nov.

– With head in full-face view, dorsolateral margin of head at most weakly marginated; lateral margin of occipital lobe and upper scrobe margin meeting as continuous curve and not forming blunt angle. Pronotum not marginated dorsolaterally ......................................................................................... 21

21. With head in full-face view, lateral margin of occipital lobe with numerous long setae freely projecting beyond margins .............................................................................................................. 22

– With head in full-face view, lateral margin of occipital lobe without any setae freely projecting beyond margins. ( Korea) .................................................... Strumigenys calvus Dong & Kim, 2020

22. Pronotal dorsum with numerous long erect simple setae. (Taiwan) ................................................... .................................................................... Strumigenys formosimonticola ( Terayama et al., 1996)

– Pronotal dorsum without long erect simple setae. ( Japan, Taiwan) .................................................... ...................................................................................... Strumigenys benten ( Terayama et al., 1996)

23. In profile view, mesosoma with numerous erect long setae ........................................................... 24

– In profile view, erect setae on mesosoma either short and stubbly, or limited to a few pairs on the mesonotum only. ............................................................................................................................. 26

24. With head in full-face view, clypeus entirely covered with scale-like obovate setae. Pronotal dorsum entirely smooth and shining. (Taiwan) .............................................. Strumigenys yamanei sp. nov.

– With head in full-face view, clypeus with stout and truncated or narrowly elliptic setae only, not scale-like obovate. Pronotal dorsum fully sculptured ..................................................................... 25

25. Leading edge of antennal scape with series of straight anteriorly projecting simple setae. Side of mesosoma entirely smooth and shining. Petiole with differentiated short anterior face. (Mainland China, Japan, Taiwan) ........................................................... Strumigenys leptothrix Wheeler, 1929

– Leading edge of antennal scape without series of straight anteriorly projecting simple setae. Side of mesosoma mostly sculptured. Petiolar peduncle grading evenly into node, petiole without differentiated short anterior face. ( Indonesia (Borneo, Sumatra), Malaysia, Philippines, Vietnam) ............................................................................... Strumigenys jacobsoni Menozzi, 1939

26. Dorsum of head with suberect to erect setae only; appressed setae, if any, limited to clypeal dorsum only. ( Vietnam) ............................................................................... Strumigenys strummeri sp. nov.

– Dorsum of head has both appressed and erect setae, appressed setae not limited to clypeal dorsum. ......................................................................................................................................................... 27

27. Side of mesosoma entirely smooth and shining ............................................................................. 28

– Side of mesosoma mostly or entirely sculptured ............................................................................ 29

28. In profile view, erect setae on mesosoma long and stout; propodeal lamellae relatively broad, broadest part slightly broader than maximum width of middle femur. Pronotum strongly marginated dorsolaterally. (Mainland China) ..................................................... Strumigenys zhenghuii sp. nov.

– In profile view, erect setae on mesosoma short and stubbly; propodeal lamellae relatively narrow, widest part much narrower than maximum width of middle femur. Pronotum at most weakly marginated dorsolaterally. ( Japan, Korea) .................................. Strumigenys alecto ( Bolton, 2000)

29. With head in profile view, dorsum without any erect seta. In full-face view, cephalic dorsum with appressed, distinctly spatulate setae; laterally-projecting setae limited to at most 1–2 around the occipital corner. (Mainland China, Thailand, Vietnam) ...................... Strumigenys doydeei sp. nov.

– With head in profile view, the dorsum with erect setae. In full-face view, cephalic dorsum with appressed fine, stout, plank-like or subspatulate setae, not distinctly spatulate; at least 4–5 laterally-projecting setae on lateral margin of occipital lobe ........................................................................ 30

30. With head in profile view, erect setae on the dorsum restricted to area between highest point of the vertex and the occipital margin ....................................................................................................... 31

– With head in profile view, erect setae present sporadically across dorsum, not restricted to area between highest point of vertex and occipital margin .................................................................... 34

31. Pronotal dorsum predominantly, strongly longitudinally or transversely striated .......................... 32

– Pronotal dorsum areolate-rugulose (reticulate-punctate), sometimes with weak longitudinal striation, not predominantly longitudinally or transversely striated .............................................................. 33

32. Pronotal dorsum predominantly, strongly longitudinally striated. (Mainland China) ........................ ..................................................................................... Strumigenys ailaoshana ( Xu & Zhou, 2004)

– Pronotal dorsum predominantly, strongly transversely striated. (Mainland China) ........................... ........................................................................................... Strumigenys nankunshana (Zhou, 2011)

33. With head in full-face view, appressed setae different in shape between dorsum and clypeus, plank-like to subspatulate setae on dorsum, and narrowly elliptic on clypeus. (Mainland China, Taiwan, Thailand) ........................................................ Strumigenys elegantula ( Terayama & Kubota, 1989)

– With head in full-face view, appressed setae similar in shape in both dorsum and clypeus, consistently stout and truncated. (Mainland China) .......................................... Strumigenys densissima sp. nov.

34. With head in full-face view, appressed setae on dorsum fine and apically-acute; lateral margin of occipital lobe with more than 7 laterally-projecting setae. ( Thailand) ............................................... .............................................................................................................. Strumigenys delicata sp. nov.

– With head in full-face view, appressed setae on dorsum stout and truncated; lateral margin of occipital lobe with at most 5–6 laterally-projecting setae. (Mainland China) .................................................. ......................................................................................................... Strumigenys intermedia sp. nov.