Key to Protanilla species

The following key is based on: [[Media:Hsu, P.W., Hsu, F.C. et al. 2017. Taxonomic notes on the genus Protanilla from Taiwan.pdf|Hsu, P.-W., Hsu, F.-C., Hsiao, Y. & Lin, C.-C. 2017. Taxonomic notes on the genus Protanilla from Taiwan. Zootaxa 4268, 117-130 (DOI 10.11646/zootaxa.4268.1.7).]]

This key does not include Protanilla schoedli and Protanilla beijingensis. The former is known from a queen while the latter was described contemporaneously with the revision that included the current key. See the notes at the end of the key for information about keying out P. beijingensi.

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1

 * Mandibles with a large convex dorsal lamella and a large longitudinal groove on outer surface (Japan) . . . . . Protanilla izanagi


 * Mandibles thin, long and narrowly triangular, without a dorsal lamella; with or without a groove on outer surface . . . . . 2

2
return to couplet #1
 * Lateral or ventral margin of mandibles with 1–2 denticles. Postpetiole broadly attached to abdominal segment IV . . . . . 3


 * Lateral and ventral margin of mandibles smooth, without denticle. Postpetiole narrowly attached to abdominal segment IV . . . . . 4

3
return to couplet #2
 * Ventral faces of mandibles with only one inconspicuous denticle. Anterior margin of abdominal segment IV in dorsal view slightly concave. Side of abdominal segment IV with a deep and narrow notch between the tergite and sternite at the anterior margin. In profile view, postpetiolar sternite nearly straight, and anterior corner forming a right angle (Taiwan) . . . . . Protanilla jongi


 * Lateroventral margins of mandibles armed with 2 distinct teeth (one long and one short). Anterior margin of abdominal segment IV in dorsal view deeply concave. Side of abdominal segment IV without a deep and narrow notch between the tergite and sternite at the anterior margin. In profile view, postpetiolar sternite deeply concave (China: Yunnan) . . . . . Protanilla furcomandibula

4
return to couplet #2
 * In full face view, anterior margin of clypeus strongly concave. In dorsal view, petiole distinctly longer than broad. Body bicol-ored, the middle portion black, the rest brownish yellow . . . . . 5


 * In full-face view, anterior margin of clypeus straight to weakly concave. In dorsal view, petiole as broad as long or broader than long. Body concolorous, uniformly yellowish brown or reddish brown . . . . . 6

5
return to couplet #4
 * In full-face view, anterior 1/3 of the head distinctly narrowed. In profile view, anterior and dorsal faces of petiolar node some-what differentiated, meeting at a broadly rounded angle. Head brownish yellow. Body small (HW 0.42–0.45 mm in types) (China: Yunnan) . . . . . Protanilla bicolor


 * In full face view, anterior half of head distinctly narrowed. In profile view, petiolar node evenly rounded, with no differentia-tion of anterior and dorsal faces. Head light black to blackish brown. Body large (HW 0.60–0.65 mm in types) (China: Yunnan) . . . . . Protanilla gengma

6
return to couplet #4
 * In profile view, anterior face of petiole distinctly concave, anterodorsal corner protruding . . . . . 7


 * In profile view, anterior face of petiole straight, sloped or slightly convex . . . . . 8

7
return to couplet #6
 * Petiole distinctly broader than long, slightly widened posteriorly. In profile view, top half of postpetiole slightly inclined ante-riorly and roughly round (Singapore and Malaysia) . . . . . Protanilla rafflesi


 * Petiole nearly square in dorsal view, as broad as long, weakly narrowed posteriorly. In profile view, top half of postpetiole roughly rectangular, with straight anterior and posterior face (India: Kerala) . . . . . Protanilla wardi

8
return to couplet #6
 * Top half of postpetiole not inclined forward, posterodorsal corner angled. In dorsal view, both petiole and postpetiole round, as long as broad . . . . . Protanilla lini


 * Top half of postpetiole strongly inclined forward. In dorsal view, at least petiole or postpetiole compressed anteroposteriorly, broader than long . . . . . 9

9
return to couplet #8
 * In full face view, anterolateral corners of head prominent and tooth-like. In profile view, petiole relatively thick and roughly trapezoidal, dorsal face long, approximately as long as anterior face . . . . . Protanilla tibeta


 * In full face view, anterolateral corners of head smooth and without prominent tooth-like structures. In profile view, petiole rel-atively thin and roughly triangular, dorsal face short, approximately half the length of anterior face . . . . . Protanilla concolor

Notes.

Protanilla schoedli Baroni Urbani & De Andrade, 2006 was described from one damaged gyne; therefore, it has been excluded from the key.

Protanilla beijingensis

Taking a specimen of this species through the current key would lead to following the second couplet of #6 (In profile view, anterior face of petiole straight, sloped or slightly convex) to couplet #8, then Protanilla lini and Protanilla beijingensis could be separated using the following couplet (as per [[Media:Man, P., Ran, H. et al. 2017. The northern-most record of Leptanillinae in China with description of Protanilla beijingensis.pdf|Man, P., Ran, H., Chen, Z., Xu, Z. 2017. The northern-most record of Leptanillinae in China with description of Protanilla beijingensis sp. nov. (Hymenoptera: Formicidae). Asian Myrmecology 9: e009008 (DOI 10.20362/am.009008).]]):


 * In profile view petiolar node relatively higher with bluntly angled anterodorsal corner. Dorsum of postpetiolar node moderately convex, subpostpetiolar process longer with anteroventral corner rounded. Body size smaller with TL 2.9 and HL 0.60. Body color yellowish brown (China: Taiwan Province) . . . . . Protanilla lini


 * In profile view petiolar node relatively lower with rounded anterodorsal corner. Dorsum of postpetiolar node almost straight, subpostpetiolar process longer with anteroventral corner rounded. Body size larger with TL 3.9 to 4.0 and HL 0.65 to 0.70. Body color reddish brown, posterior half of mesothorax and metathorax black (China: Beijing) . . . . . Protanilla beijingensis