Carebara Westwood, 1840

Liu, Zhi-yu, Zhong, Ying, Huang, Yu-yuan, Ran, Hao & Song, Fan, 2024, A new ant species of the genus Carebara Westwood, 1840 (Hymenoptera, Formicidae, Myrmicinae) with a key to Chinese species, ZooKeys 1190, pp. 1-37 : 1

Genus Carebara Westwood, 1840

Carebara Carebara Westwood, 1840: 86. Type species: Carebara lignata Westwood, 1840: 86, Indonesia (Java). Indomalaya.

Pheidologeton = Pheidologeton Mayr, 1862: 750. Synonymized by Fischer et al. 2014: 63.

Oligomyrmex = Oligomyrmex Mayr, 1867: 110. Synonymized by Fernández 2004: 194.

Aeromyrma = Aeromyrma Forel, 1891: 198. Synonymized by Fernández 2004: 194.

Aneleus = Aneleus Emery, 1900: 327. Synonymized by Fernández 2004: 194.

Erebomyrma = Erebomyrma Wheeler, 1903: 138. Synonymized by Fernández 2004: 194.

Paedalgus = Paedalgus Forel, 1911: 217. Synonymized by Fernández 2004: 194.

Lecanomyrma = Lecanomyrma Forel, 1913: 56. Synonymized by Fernández 2004: 194.

Spelaeomyrmex = Spelaeomyrmex Wheeler, 1922: 9. Synonymized by Fernández 2004: 194.

Hendecatella = Hendecatella Wheeler, 1927: 93. Synonymized by Fernández 2004: 194.

Amauromyrmex = Amauromyrmex Wheeler, 1929: 1. Synonymized by Fischer et al. 2014: 63.

Solenops = Solenops Karavaiev, 1930: 207. Synonymized by Fernández 2004: 194.

Idrisella = Idrisella Santschi, 1937: 372. Synonymized by Fischer et al. 2014: 66.

Crateropsis = Crateropsis Patrizi, 1948: 174. Synonymized by Fernández 2004: 194.

Sporocleptes = Sporocleptes Arnold, 1948: 219. Synonymized by Fernández 2004: 194.

Nimbamyrma = Nimbamyrma Bernard, 1953: 240. Synonymized by Fernández 2004: 194.

Afroxyidris = Afroxyidris Belshaw & Bolton, 1994: 631. Synonymized by Fernández 2004: 194.

Neoblepharidatta = Neoblepharidatta Sheela & Narendran, 1997: 88. Synonymized by Fernández 2004: 194.

Parvimyrma = Parvimyrma Eguchi & Bui, 2007: 40. Synonymized by Fernández 2010: 195.

Synopsis of members of Carebara from China.

Currently, there are 36 Carebara species and subspecies in China, with the majority in the southern and southwestern regions (Fig. 1 ). The highest diversity is observed in Guangdong, Guangxi, Yunnan, and Sichuan provinces ( Xu 2003; Zhou and Zheng 1997).

Here we provide a brief overview of the provisional definition of Chinese Carebara species groups. In addition to the former Pheidologeton species, other Carebara members in China (except C. amia ) align with the Carebara concinna-lignata group proposed by Bharti. It is worth mentioning that the criteria for classification vary among different studies. Bharti and Kumar (2013) suggested merging the Carebara concinna and Carebara lignata groups, while Fischer et al. (2015) retained the Carebara lignata group, defining its features based on Fernández (2004): workers typically small with 9-segmented antenna, mandibles 3- or 4-toothed, absent eyes and propodeal teeth, and a rounded dorsum of the propodeum. The queens are generally much larger than the workers. Hosoishi et al. (2022) established the Carebara acutispina group; however, it is highly probable that this is an artificial group within the Carebara concinna - Carebara lignata group. Due to the lack of comprehensive revisions of all castes (especially queens and males), the current definition of species groups relies predominantly on the morphology of the worker caste. However, this approach introduces uncertainties due to the potential influence of convergent evolution and a global investigation into Carebara species, utilizing molecular data, is imperative for a more accurate understanding of the phylogenetic relationship between groups. To prevent the proposal of multiple species groups, our definition is mainly based on Bharti and Kumar (2013).

There are 11 species and subspecies of China belonging to the previously valid genus Pheidologeton : C. affinis (Jerdon, 1851), C. diversa (Jerdon, 1851), C. diversa draco (Santschi, 1920), C. diversa laotina (Santschi, 1920), C. latinoda , C. melasolena , C. nanningensis , C. trechideros , C. vespillo , C. yanoi , C. zengchengensis . These species are identified by their 11-segmented antennae, distinct polymorphic worker castes, and multifaceted eyes ( Fischer et al. 2015). Fischer et al. (2014) indicated that former Pheidologeton species would be split into two groups: one with a polymorphic worker caste and the other with a dimorphic worker caste, and the 11 Chinese taxa mentioned above belong to the former group.

The Carebara lignata group was originally established by Fernández (2004) to group New World species characterized by minor workers with 9-segmented antenna and the absence of eyes. The minor workers of this group mainly lack propodeal spines. Major workers present or absent. Members of the Carebara concinna group with dimorphic workers, eyes present in both major and minor workers, propodeum armed or only angulated, antenna 9- to 11- (rarely 8-) segmented. Bharti and Kumar (2013) suggested redefining the Carebara concinna group including the Carebara lignata group; this alteration was based on the observation that the major worker of C. asina aligned with the Carebara concinna group, whereas the minor worker lacked eyes and propodeal spines, consistent with the traditional Carebara lignata group proposed by Fernández (2010).

Certain Chinese Carebara species, like C. bihornata and C. sakamotoi , also form a bridge between the Carebara lignata and Carebara concinna groups. Similar to C. asina , C. bihornata exhibit eyeless minor workers with an unarmed propodeum, while the major workers accord with the features of Carebara concinna group. Some species provide additional insights into the Carebara concinna - Carebara lignata group, such as C. capreola and C. curvispina , both characterized by eyeless major and minor workers. This suggests that the features of the Carebara concinna - Carebara lignata group include: (1) workers monomorphic or dimorphic; (2) antenna 9- to 11- (rarely 8-) segmented; (3) propodeal spines present or absent in major and minor workers; (4) eyes present or absent in major and minor workers.

Key to Carebara species of China based on major worker caste

This key is based on Xu (2003) and Zhou et al. (2006), including 34 species and subspecies; some illustrations of the key were drawn from Xu (2003) and Terayama (1996). The following species are excluded from this key because descriptions of the major workers are unavailable: C. amia , C. castanea , and C. lignata . Some distribution data about Chinese Carebara species in previous studies are ambiguous. After verification with Xu (pers. comm. July 21, 2023), some records are not accepted in this study and the following species are excluded from the Chinese fauna: C. asina , C. bengalensis (Forel, 1902), C. bruni (Forel, 1913), C. cribriceps (Wheeler, 1927), and C. pumilia Fischer et al., 2014.

1	Antenna 11-segmented (Fig. 2A )	2
-	Antenna 9- or 10-segmented (Fig. 2B, C )	17
2	Worker caste polymorphic, with continuous series of intermediates between minor and largest major worker	3
-	Worker caste dimorphic	13
3	Propodeal spines long,> 1/2 of the distance between the base of two spines (Fig. 3A )	4
-	Propodeal spines short, <1/3 of the distance between the base of 2 spines (Fig. 3B )	9
4	Largest major worker with mesoscutellum strongly convex in lateral view and with single ocellus on the front of head (Fig. 4A, C )	5
-	Largest major worker with mesoscutellum broadly convex in lateral view and with no ocelli on the front of head (Fig. 4B, D )	7
5	Largest major worker distinctly smaller with TL 11-12 mm	C. diversa draco (Santschi, 1920)
-	Largest major worker distinctly larger with TL ~ 16 mm	6
6	The posterior quarter of the head with transverse and very large wrinkles; the smooth frontal space more extensive (Fig. 5A )	C. diversa laotina (Santschi,1920)
-	The posterior 1/3 of head with diverged wrinkles; smooth frontal space more narrowed (Fig. 5B )	C. diversa (Jerdon)
7	Propodeal spines curving forward and inclined (Fig. 6A )	C. yanoi (Forel)
-	Propodeal spines directed backwards or erect (Fig. 6B )	8
8	Promesonotum slightly convex in lateral view; first tergite of gaster> 2 × as wide as second tergite	Carebara nanningensis (Li & Tang)
-	Promesonotum distinctly convex in lateral view; first gastric tergum almost as wide as second tergum	C. affinis (Jerdon)
9	Head and body mostly smooth and shiny (Fig. 7A )	10
-	Head and body coarsely striate (Fig. 7B )	12
10	Propodeal spines pointing backwards in the largest major worker; petiolar node broadly rounded above in profile view; head without a coarse black line in median longitudinal groove (Fig. 8A, C )	C. latinoda (Zhou & Zheng)
-	Propodeal spines curving forward in the largest major worker; petiolar node narrowed above, triangular in profile view; head with a coarse black line in median longitudinal groove (Fig. 8B, D )	11
11	Postpetiole approximately as long as wide; hairs sparse (Fig. 9A, C )	C. vespillo (Wheeler)
-	Postpetiole distinctly broader than long; hairs abundant (Fig. 9B, D )	C. melasolena (Zhou & Zheng)
12	Propodeal spines laterally compressed and curving forward; mandibles with longitudinal striations on the base in full-face view; interspaces on the head between striations punctured (Fig. 10A, C )	C. trechideros Zhou & Zheng
-	Propodeal spines thick and straight, not curved; mandibles smooth in full-face view; interspaces between striations smooth (Fig. 10B, D )	C. zengchengensis (Zhou et al.)
13	Mandible with 5 teeth on masticatory margin (Fig. 11A )	14
-	Mandible with 6 teeth on masticatory margin (Fig. 11B )	16
14	Posterolateral corners of head with minute tubercles; eyes present; head slightly longer than wide (Fig. 12A )	C. altinodu s (Xu)
-	Posterolateral corners of head with developed horns; eyes absent; head distinctly longer than wide (Fig. 12B )	15
15	Head broader behind than in front with more punctures; head and thorax with dense hairs	C. capreola (Wheeler)
-	The posterior portion of head almost as wide as the anterior portion; head with less punctures, smoother and more shiny; head and thorax with sparser and shorter hairs	C. capreola laeviceps (Wheeler)
16	Eyes absent; propodeal denticles downwardly inclined; first segment of gaster finely punctuate (Fig. 13A )	C. curvispina (Xu)
-	Eyes present; propodeal denticles dorsoposteriorly pointed; first segment of gaster densely longitudinally striate (Fig. 13B )	C. striata (Xu)
17	Mandible with 6 teeth on masticatory margin (Fig. 14C )	18
-	Mandible with 4 or 5 teeth on masticatory margin (Fig. 14A, B )	19
18	HL <1 mm; first gastral tergum smooth and shiny	C. oni (Terayama)
-	HL> 1 mm; first gastral tergum punctate and microreticulate with longitudinal striations (Fig. 15A, B )	C. qianliyan Terayama
19	Posterolateral corners of head with a pair of distinct horns or small tubercles (Fig. 16A, B )	20
-	Head with no horns or tubercles (Fig. 16C )	29
20	Propodeum with a pair of protruding denticles (Fig. 17A )	21
-	Propodeum without a pair of protruding denticles; posterodorsal corner of propodeum rounded or forms an obtuse or right angle (Fig. 17B, C )	23
21	Posterior area of head without transverse striations; metanotal groove impressed shallowly; body smaller with TL 1.4 mm (Fig. 18C )	C. acutispina (Xu)
-	Posterior area of head with transverse striations; metanotal groove deeply impressed; body larger with TL 2.1-2.6 mm (Fig. 18A, B )	22
22	Mandible with 4 teeth on masticatory margin; clypeus with the anterior margin of median portion concave indistinctly	Carebara wheeleri (Ettershank)
-	Mandible with 5 teeth on masticatory margin; clypeus with the anterior margin of median portion concave distinctly	C. obtusidenta (Xu)
23	Horns connected by a developed transverse ridge (Fig. 19A )	24
-	Horns not connected by a developed transverse ridge (Fig. 19B )	25
24	Head capsule thin with straight anterior margin in lateral view (Fig. 20A )	C. bihornata (Xu)
-	Head capsule thick with convex anterior margin in lateral view (Fig. 20B )	C. sakamotoi Terayama et al.
25	Body larger with TL 3.0-3.5 mm	C. polyphemus (Wheeler)
-	Body smaller with TL 1.5-2.3 mm	26
26	Mandible with 4 teeth on masticatory margin	C. taiponica (Wheeler)
-	Mandible with 5 teeth on masticatory margin	27
27	Head coarsely microreticulate; frons and vertex with many striae (Fig. 21A )	C. yamatonis (Terayama)
-	Head largely smooth and shiny (Fig. 21B )	28
28	Anterodorsal corner of propodeum prominent, forming an acute tooth behind metanotal groove (Fig. 22A )	C. sauteri (Forel)
-	Anterodorsal corner of propodeum not forming an acute tooth (Fig. 22B )	C. rectidorsa (Xu)
29	Head nearly square, ~ as long as broad; eyes with 16 facets; head with 3 ocelli; dorsum of mesosoma straight (Fig. 23A, B )	C. hunanensis (Xu)
-	Head rectangular, longer than broad; eyes with <10 facets; head without ocelli; dorsum of mesosoma not straight	30
30	Propodeum with a pair of acute teeth; head with fine reticulations	C. reticapita (Xu)
-	Propodeum forms an obtuse angle; head smooth, at most sparsely punctured	31
31	Posterodorsal corner of propodeum forming a right angle of ~ 90° (Fig. 24A )	C. pseudolusciosa (Wu & Wang)
-	Posterodorsal corner of propodeum forming an obtuse angle of more than 90° (Fig. 24B )	32
32	Vertex with transverse striations	C. jiangxiensis (Wu & Wang)
-	Vertex smooth and with no striations	33
33	Antenna 10-segmented; katepisternum rugose-reticulate; body distinctly larger with TL> 2.6 mm (Fig. 25A )	C. laeviceps sp. nov.
-	Antenna 9-segmented; katepisternum smooth and shiny; body smaller with TL ~ 2 mm (Fig. 25B )	C. lusciosa (Wheeler)

Figures

Figure 1. Map of the diversity of known Chinese Carebara species. Shades from pale to dark indicate species numbers from low to high.

Figure 2. Antenna A 11 - segmented B 9 - segmented C 10 - segmented.

Figure 3. Mesosoma A longer spine B shorter spine.

Figure 4. Head in full-face view and mesosoma in lateral view (the largest major worker) A head with an ocellus B head with no ocelli C mesoscutellum strongly convex D mesoscutellum broadly convex.

Figure 5. Heads of C. diversa and C. diversa laotina in full-face view (the largest major worker) A C. diversa laotina, head with broader smooth space, wrinkles mostly transverse B C. diversa, head with more narrowed smooth space, wrinkles fine and diverged.

Figure 6. Pronotal spines A curving forward B backwards.

Figure 7. Head in full-face view A head mostly smooth and shiny B head mostly striate.

Figure 8. Head in full-face view, mesosoma and petiole in lateral view A head without a coarse black line B head with a coarse black line in median longitudinal groove C propodeal spines pointing backward, petiolar node round above D propodeal spines curving forward, petiolar node narrowed above.

Figure 9. Head and mesosoma in lateral view, postpetiolar node in dorsal view A C. vespillo, hairs sparse B C. melasolena, hairs abundant C C. vespillo, postpetiolar node nearly as long as wide D C. melasolena, postpetiolar node distinctly wider than long.

Figure 10. Head in full-face view and mesosoma in lateral view (the largest major worker) A head of C. trechideros, mandibles with longitudinal striations, interspaces between striations punctured B head of C. zengchengensis, mandibles without striations, interspaces between striations smooth C propodeal spines curving forward D propodeal spines straight and not curved.

Figure 11. Mandibles A mandible with 5 teeth B mandible with 6 teeth.

Figure 12. Horns A posterolateral corners of head with minute tubercles B posterolateral corners of head with developed horns.

Figure 13. Two Carebara species in lateral view A C. curvispina, propodeal denticles down-inclined, first segment of gaster finely punctuate, eyes absent B C. striata, propodeal denticles dorsoposteriorly pointed, first segment of gaster densely longitudinally striate, eyes present.

Figure 14. The number of teeth A 4 - teethed B 5 - teethed C 6 - teethed.

Figure 15. Head in full-face view and tergum in lateral view (C. qianliyan) A HL> 1 mm B first gastral tergum punctate with longitudinal striations.

Figure 16. Horns or tubercles on the posterior corner of head A distinct horns B small tubercles C no horns or tubercles.

Figure 17. Propodeum in lateral view A propodeum with protruding denticles B propodeum forming an obtuse angle C propodeum rounded.

Figure 18. Striations and metanotal groove A head with transverse striations B metanotal groove impressed deeply C metanotal groove impressed shallowly.

Figure 19. Horns in dorsal view A horns connected by a transverse ridge B horns not connected by a transverse ridge.

Figure 20. Head capsule in lateral view A head capsule thin with anterior margin straight B head capsule thick with anterior margin convex.

Figure 21. Head in full-face view A head with dense microreticulation B head largely smooth and shiny.

Figure 22. Mesosoma in lateral view A anterodorsal corner of propodeum forming an acute tooth B anterodorsal corner of propodeum not forming an acute tooth.

Figure 23. C. hunanensis A head with 3 ocelli in full-face view B dorsum of mesosoma straight in lateral view.

Figure 24. Propodeum in lateral view A posterodorsal corner forming an right angle B posterodorsal corner forming an obtuse angle.

Figure 25. Katepisternum in lateral view A katepisternum rugose-reticulate B katepisternum smooth.