Revised worker key to the East Asian species of Ponera

The worker key to East Asian Ponera species is modified and updated based on the previous keys and species descriptions provided in Wheeler (1928a, b), Taylor (1967); Xu (2001a, b), Zhou (2001), Terayama (1986, 1996, 2009), Wang et al. (2009) and Yoshimura et al. (2009).

The key provides general directions for the identification of Ponera species in Eastern Asia. However, due to a potentially high number of undescribed species in the region, the readers should refer to specific species diagnoses to confirm their identification.

Head width (HW), which has been widely used for diagnosis in past studies, and which is positively correlated with body size (e.g. Taylor 1967, Terayama 1996), is an important identification aid. We plotted mean and range of HW for all the species included in this study (Figure 5). The simultaneous use of the key and figure 5 is suggested.

1a. In lateral view, petiolar node very thick with convex posterior margin; with upper portion of posterior margin bulging (Fig. 6A).................................................................................................... 2

1b. In lateral view, petiolar node not as developed and presenting straight to convex posterior margin; with upper portion of poste- rior margin not bulging (Fig. 6B, C)...................................................................... 3

2a. Petiolar node in dorsal view with slightly convex anterior margin and slightly concave posterior margin (Fig. 7A). Smaller species, HW: 0.54–0.60 mm. Body color dark.............................................. P. rishen Terayama, 2009

2b. Petiolar node in dorsal view with strongly convex anterior margin and strongly concave posterior margin (Fig. 7B). Larger species, HW: 0.65–0.75 mm. Body color reddish brown.................................... P. takaminei Terayama, 1996

3a. Eye large, each consisting of 20 or more facets (Fig. 8A). Larger species, HW: ca. 0.68 mm ..... P. kohmoku Terayama, 1996 3b. Eye small, each consisting of 10 or fewer facets (Fig. 8B). Size variable.......................................... 4

4a. Masticatory margin of mandible with 5 subequal large teeth (Fig. 9A). Smaller species, HW: 0.53–0.55 mm ............................................................................................... P. pentodontos Xu, 2001a

4b. Masticatory margin of mandible with 3 enlarged apical teeth followed by a series of small to indistinct denticles (Fig. 9B). Size variable............................................................................................. 5 5a. Antennal scape, when laid backward, exceeding posterior margin of head in full-face view (Fig. 10A).................. 6 5b. Antennal scape, when laid backward, not exceeding posterior margin of head in full-face view (Fig. 10B)............... 8 6a. Scape exceeding posterior border of head by nearly 34% of scape length............... P. hubeiensis Wang & Zhou, 2009 6b. Scape exceeding posterior border of head by <10% of scape length.............................................. 7 7a. Petiolar node in lateral view with straight posterior margin (Fig. 11A). HW: 0.58–0.65 mm ....... P. alisana Terayama, 1986 7b. Petiolar node in lateral view with convex posterior margin (Fig. 11B). HW: 0.61–0.70 mm ....... P. chapmani Taylor, 1967

8a. Petiolar node in dorsal view subrectangular or subtrapezoidal, anterior and lateral margins not forming a single arch (Fig. 12A, B: the dotted line not forming a continuously circular arc; lateral margins present), with slightly convex or almost straight anterior margin........................................................................................... 9

8b. Petiolar node in dorsal view semi-circular or oval, anterior and lateral margins constituting a single arch (Fig. 12C, D: the dotted line forming a continuously circular arc), with distinctly convex anterior margin................................ 12

9a. Dorsum of petiolar node in lateral view convex and relatively acute, with broadly convex posterior margin (Fig. 13A)............................................................................................. P. terayamai sp. n.

9b. Dorsum of petiolar node in lateral view slightly convex, blunt, with straight and sloping posterior margin (Fig. 13B, C).... 10

10a. Subpetiolar process with large posteroventral teeth and large circular fenestra (Fig. 13B). Larger species, HW: 0.39–0.43 mm. Body color dark brown......................................................... P. chiponensis Terayama, 1986

10b. Subpetiolar process with small or indistinct posteroventral teeth, and small circular fenestra (Fig. 13C). Smaller species, HW: Ĺ 0.35 mm. Body color yellowish brown.................................................................. 11

11a. Petiolar node in dorsal view rectangular, broader than long, with slightly convex anterior margin (Fig. 14A). Larger species, HW: ca. 0.33 mm ........................................................................ P. baka Xu, 2001a

11b. Petiolar node in dorsal view subquadrate, about as wide as long, with straight anterior margin (Fig. 14B). Smaller species, HW: 0.27–0.28 mm .................................................................. P. shennong Terayama, 2009 12a. Subpetiolar process without developed posteroventral teeth (Fig. 15A).......................................... 13 12b. Subpetiolar process with developed posteroventral teeth (Fig. 15B)............................................. 16

13a. Metanotal groove in lateral view indistinctly or weakly incised (Fig. 16A). Petiolar node in lateral view anterior and posterior margins converging, not parallel......................................................................... 14

13b. Metanotal groove in lateral view deeply and broadly incised (Fig. 16B). Petiolar node in lateral view with parallel anterior and posterior margins................................................................. P. nangongshan Xu, 2001a

14a. In full-face view, posterior margin of head distinctly concave (Fig. 17A). Petiolar node in lateral view thick (LPeI: 63), with sloping and straight posterior margin. Smaller species, HW: ca. 0.35 mm. Body yellowish brown...... P. xantha Xu, 2001b

14b. In full-face view, posterior margin of head slightly concave or straight (Fig. 17B, C). Petiolar node in lateral view relatively thin (LPeI: ca. 50), with almost vertical and slightly convex posterior margin. Larger species, HW ± 0.40 mm. Body brown to dark brown.......................................................................................... 15

15a. Petiolar node in dorsal view oval, with slightly convex posterior margin (Fig. 18A). Larger species, HW: ca. 0.53 mm ........................................................................................... P. bawana Xu, 2001b

15b. Petiolar node in dorsal view arched, with straight posterior margin (Fig. 18B). Smaller species, HW: ca. 0.40 mm ......................................................................................... P. yuhuang Terayama, 2009

16a. Length of 8 th antennal segment as long as 7 th antennal segment (Fig. 19A) Metanotal groove indistinctly incised. Smaller spe- cies, HW: 0.30–0.31 mm ............................................................... P. szaboi Wilson, 1957

16b. Length of 8 th antennal segment ± 1.5 times length of 7 th antennal segment (Fig. 19B)............................... 17 17a. Metanotal groove in dorsal view indistinctly incised or almost obliterated (Fig. 20A)............................... 18 17b. Metanotal groove in dorsal view weakly incised (Fig. 20B)................................................... 22

18a. Petiolar node in dorsal view oval, with convex posterior margin (Fig. 21A). Smaller species, HW: ca. 0.45 mm ............................................................................................... P. longlina Xu, 2001a

18b. Petiolar node in dorsal view not oval, with straight to slightly concave posterior margin (Fig. 21B, C, D). Larger species, HW ± 0.49 mm .......................................................................................... 19 19a. Side of propodeum with weak to strong striae and hairs in lateral view (Fig. 22A, B, C). Body color variable. Larger species, HW ± 0.55 mm ...................................................................................... 20

19b. Side of propodeum shining and smooth (Fig. 22D). Body color reddish brown. Smaller species, HW: 0.49–0.52 mm ................................................................................................... P. wui sp. n.

20a. Lateral faces of metapleuron and propodeum weakly striate (Fig. 22 AC)......................................... 21

20b. Lateral faces of metapleuron and propodeum strongly striate (Fig. 22B)........................ P. menglana Xu, 2001a

21a. Apex of antennal scape, when laid backward, with a remaining distance to the posterolateral corner of ca. 10% of the scape length. Lateral faces of metapleuron and propodeum weakly striate (Fig. 22C)................ P. paedericera Zhou, 2001

21b. Apex of antennal scape, when laid backward, with a remaining distance to the posterolateral corner of Ĺ 5% of the scape length. Metapleuron and propodeum with relatively strong striae and abundant hairs in lateral view (Fig. 22A)............................................................................................. P. scabra Wheeler, 1928b

22a. Anterodorsal corner of petiolar node in lateral view protruding forward (Fig. 23A)................. P. diodonta Xu, 2001b

22b. Anterodorsal corner of petiolar node in lateral view not protruding forward (Fig. 23B, C, D)......................... 23

23a. Apex of antennal scape, when laid backward, with a remaining distance to the posterolateral corner of Ĺ 5% of the scape length................................................................................................... 29

23b. Apex of antennal scape, when laid backward, with a remaining distance to the posterolateral corner of ± 10% of the scape length.............................................................................................. 24

24a. Dorsum of petiolar node in lateral view convex without forming distinct angle on posterodorsal corner; anterodorsal corner clearly much higher than posterodorsal corner (Fig. 24 AB).................................................... 25

24b. Dorsum of petiolar node in lateral view slightly convex without forming distinct angle on posterodorsal corner; anterodorsal corner slightly higher, or as high as posterodorsal corner (Fig. 24 CDEF)......................................... 26

25a. Third abdominal tergum distinctly longer than broad in dorsal view (ATI ± 105).............. P. bishamon Terayama, 1996 25b. Third abdominal tergum broader than long in dorsal view (ATI Ĺ 96).......................... P. pianmana Xu, 2001b 26a. Petiolar node in dorsal view relatively thicker (Fig. 25A)..................................................... 27 26b. Petiolar node in dorsal view relatively thin (Fig. 25B)........................................................ 28

27a. Petiolar node in dorsal view relatively thin (Fig. 24E). Posterior margin of head slightly concave (Fig. 26A). Clypeus without distinct median tooth............................................................... P. incerta (Wheeler, 1933)

27b. Petiolar node in lateral view relatively thicker (Fig. 24F). Posterior margin of head more concave (Fig. 26B). Clypeus with distinct median tooth present (observation of the specimen using various angles needed)........ P. taiyangshen Terayama, 2009

28a. Posterior margin of head concave (Fig. 27A). Anterior margin of petiolar node in dorsal view well convex (Fig. 25C). Larger species, HW: 0.41–0.50 mm. Body color brown......................................... P. japonica Wheeler, 1906 28b. Posterior margin of head almost straight (Fig. 27B). Anterior margin of petiolar node in dorsal view well convex (Fig. 25D). Smaller species, HW: 0.32–0.34 mm. Body color yellowish brown......................... P. swezeyi (Wheeler, 1933)

29a. Petiolar node in lateral view with strongly convex posterior margin (Fig. 28A, B). Petiolar node in dorsal view with concave posterior margin, and large portion of the declivity clearly visible (Fig. 29A, B)................................... 30

29b. Petiolar node in lateral view with straight to slightly convex posterior margin (Fig. 28C, D). Petiolar node in dorsal view with straight or slightly concave posterior margin, and small portion of the declivity visible (Fig. 29C, D)................... 31

30a. Petiolar node in lateral view with broadly convex posterior margin (Fig. 28A). Petiolar node in dorsal view thin (Fig. 29A). Body color dark brown............................................................ P. sinensis Wheeler, 1928a

30b. Petiolar node in lateral view with convex posterior margin (Fig. 28B). Petiolar node in dorsal view relatively thicker (Fig. 29B). Body color lighter brown...................................................... P. tamon Terayama, 1996

31a. Posterodorsal corner of petiolar node forming a blunt angle in lateral view (Fig. 30A specimen collected in Sarawak, Malaysia; also see Taylor 1967, Fig. 71). Subpetiolar process with small posteroventral teeth.............. P. oreas (Wheeler, 1933)

31b. Posterodorsal corner of petiolar node convex in lateral view (Fig. 30B specimen collected in Vietnam; also see Zhou 2001, Fig. 74). Subpetiolar process with larger posteroventral teeth.................................. P. guangxiensis Zhou, 2001