Research Article |
Corresponding author: Michael Staab ( michael.staab1@tu-darmstadt.de ) Academic editor: Marek Borowiec
© 2015 Michael Staab.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Staab M (2015) Aenictus hoelldobleri sp. n., a new species of the Aenictus ceylonicus group (Hymenoptera, Formicidae) from China, with a key to the Chinese members of the group. ZooKeys 516: 137-155. https://doi.org/10.3897/zookeys.516.9927
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Aenictus is the most species-rich genus of army ants in the subfamily Dorylinae and one of the most species rich ant genera in China and the world. In this paper, a new species of the Aenictus ceylonicus group, Aenictus hoelldobleri sp. n., is described and illustrated based on the worker caste. The new species occurs in the subtropical forests of south-east China and is morphologically most similar to A. henanensis Li & Wang, 2005 and A. wudangshanensis Wang, 2006. Aenictus hoelldobleri sp. n. can be distinguished from both species by the shape of the subpetiolar process. The new species also resembles Aenictus lifuiae
Army ants, Dorylinae , Gutianshan National Nature Reserve, species descriptions, subtropical forest, taxonomy
Army ants form a monophyletic group in the subfamily Dorylinae (
Of all army ant genera the genus Aenictus is the most species rich and widely distributed. Currently, 181 valid species (
Over the last years, in a series of significant papers Weeyawat Jaitrong, Seiki Yamane, and co-workers divided the south-east Asian Aenictus fauna in 12 species groups based on the worker caste (
In the present paper Aenictus hoelldobleri Staab sp. n. is described, a new species of the A. ceylonicus group from the subtropical forests of south-east China. Furthermore, the first Chinese record of A. watanasiti Jaitrong & Yamane, 2013 is reported, and new Chinese locality records for A. formosensis Forel, 1913, A. fuchuanensis Zhou, 2001, A. thailandianus Terayama & Kubota, 1993, and A. wudangshanensis Wang, 2006 are added. As the key from
All morphological observations were made with a Leica SD6 stereomicroscope, which was equipped with an ocular micrometer to take measurements. Automontage images of specimens were provided by http://www.antweb.org/ (photographer: Michele Esposito) or extracted from
The general worker terminology as well as abbreviations used for measurements and indices follow
CI Cephalic index, HW / HL × 100.
HL Maximum head length in full-face view, measured from the midpoint of the anterior clypeal margin to the midpoint of the posterior margin of the head.
HW Maximum head width in full-face view.
ML Mesosomal length measured from the point at which the pronotum meets the cervical shield to the posterior base of the metapleuron in profile.
PL Petiole length measured from the anterior margin of the peduncle to the posteriormost point of the petiolar tergite in profile.
SI Scape index: SL / HW × 100.
SL Scape length excluding the basal constriction and condylar bulb.
TL Total length, measured roughly from the anterior margin of head to the tip of gaster in fully stretched specimens in profile.
CASC California Academy of Science Collection, San Francisco, California, USA.
HLMD Hessisches Landesmuseum Darmstadt, Darmstadt, Germany.
IZAS Insect Collection of the Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
ZMBH Museum für Naturkunde, Berlin, Germany.
Distribution maps for all Chinese A. ceylonicus group species were composed from the locality records given in the original descriptions, the records presented in this paper and the records listed in
Diagnosis.
Antenna 10-segmented; scape reaching or extending beyond half of head length, but not reaching the occipital corner of head in full-face view. Mandible linear; its basal and lateral margins almost parallel; masticatory margin with large apical tooth followed by medium-sized subapical tooth; between subapical tooth and basal tooth 0–6 small denticles present. With mandibles closed, a gap present between mandibles and anterior margin of clypeus. Anterior clypeal margin weakly concave or almost straight, lacking denticles. Frontal carina short and thin, reaching or slightly extending beyond the level of posterior margin of torulus; anterior curved extension of frontal carina reaching or extending beyond the level of anterior clypeal margin in full-face view; parafrontal ridge absent. Promesonotum usually convex dorsally and sloping gradually to propodeum. Subpetiolar process developed. Head and first gastral tergite smooth and shiny. Body yellowish, reddish or dark brown; typhlatta spot absent.
Remarks. The A. ceylonicus group can be easily distinguished from other Aenictus species groups by the combination of linear mandibles, the presence of a gap between the closed mandibles and the anterior clypeal margin, and an almost straight or feebly concave anterior clypeal margin, which lacks denticles.
Aenictus formosensis Forel, 1913 (Taiwan, Zhejiang)
Aenictus fuchuanensis Zhou, 2001 (Guangxi, Hong Kong, Jiangxi)
Aenictus henanensis Li & Wang, 2005 (Henan)
Aenictus hoelldobleri sp. n. (Jiangxi, Zhejiang)
Aenictus lifuiae Terayama, 1984 (Taiwan)
Aenictus maneerati Jaitrong & Yamane, 2013 (Yunnan)
Aenictus thailandianus Terayama & Kubota, 1993 (Yunnan, Guizhou)
Aenictus watanasiti Jaitrong & Yamane, 2013 (Guizhou)
Aenictus wudangshanensis Wang, 2006 (Hubei, Zhejiang)
Aenictus yangi Liu, Hita Garcia, Peng & Economo, 2015 (Yunnan)
Key to Chinese A. ceylonicus group species based on the worker caste, modified and updated after the key of
1 | Mandible with 2-6 teeth/denticles between subapical and basal teeth (mandible with more than 4 teeth/denticles) (Fig. |
2 |
– | Mandible with 0-1 tooth/denticle between subapical and basal teeth (mandible with 3-4 teeth/denticles) (Fig. |
7 |
2 | Promesonotum entirely punctate (Fig. |
A. thailandianus Terayama & Kubota |
– | Promesonotum predominantly smooth and shiny (Fig. |
3 |
3 | Subpetiolar process weakly developed, low and rounded, not rectangular (Fig. |
4 |
– | Subpetiolar process well developed and rectangular (Figs |
5 |
4 | Dorsum of propodeum straight in profile, entirely microreticulate and opaque; promesonotum microreticulate except posterior half of pronotum smooth and shiny; masticatory margin of mandible with large apical tooth, followed by a small preapical tooth, and 5 minute denticles (Henan) | A. henanensis Li & Wang |
– | Dorsum of propodeum weakly convex to almost straight in profile, punctate but somewhat shiny; promesonotum entirely smooth and shiny except for reticulate anteriormost portion (Fig. |
A. lifuiae Terayama |
5 | Dorsum of mesonotum and petiolus entirely smooth and shiny (Fig. |
A. yangi Liu, Hita Garcia, Peng & Economo |
– | Dorsum of mesonotum and petiolus finely reticulate (Fig. |
6 |
6 | Subpetiolar process rectangular-trapezoidal, its ventral outline with a thin almost transparent lamellae (Fig. |
A. hoelldobleri sp. n. |
– | Subpetiolar process rectangular, its apex very acute and directed downwards medially (Fig. |
A. wudangshanensis Wang |
7 | Mandible with 3 teeth including apical and basal tooth (Fig. |
A. watanasiti Jaitrong & Yamane |
– | Mandible with 4 teeth including apical and basal tooth (Fig. |
8 |
8 | Subpetiolar process well-developed, subrectangular with convex ventral lamella, and with anterior and posterior corners acutely or bluntly angulated (Fig. |
A. formosensis Forel |
– | Subpetiolar process weakly developed or very low (Fig. |
9 |
9 | Subpetiolar process very low, with anterior and posterior denticles that protrude downwards (Fig. |
A. maneerati Jaitrong & Yamane |
– | Subpetiolar process weakly developed, in profile its ventral outline almost straight or weakly convex, without denticles (Fig. |
A. fuchuanensis Zhou |
Head of Chinese A. ceylonicus group species in full face view. A A. yangi B A. formosensis (CASENT0914926) C A. fuchuanensis (CASENT0914926) D A. maneerati. Scale bars – 0.2 mm. Image A is from
Mesosoma and waist segments of Chinese A. ceylonicus group species in dorsal view. A A. thailandianus B A. lifuiae C A. yangi D A. hoelldobleri sp. n. (CASENT0914932).
Mesosoma and waist segments of Chinese A. ceylonicus group species in profile. A A. thailandianus B A. lifuiae C A. hoelldobleri sp. n. (CASENT0914932) D A. wudangshanensis (CASENT0914927) E A. formosensis F A. fuchuanensis G A. maneerati. Scale bars – 0.5 mm. Images C and D are from http://www.antweb.org (photographer: Michele Esposito). All other images are from
Worker from CHINA, Jiangxi Province, near the village Xingangshan, ca. 15 km SE of Wuyuan, 29°4'39"N / 117°55'20"E, 300 m asl, 6.VII.2013, hand collection on ground, leg. Michael Staab, label “MS1647”, deposited in IZAS.
20 workers in total, all with the same data as holotype (3 in CASC: CASENT0914931, CASENT0914932, CASENT0914933, 4 in HLMD, 10 in IZAS, 3 in ZMBH).
Holotype: TL 2.88, HL 0.65, HW 0.57, SL 0.46, ML 0.95, PL 0.25, CI 88, SI 81. Paratypes (n=20 measured): TL 2.34-2.88, HL 0.52-0.68, HW 0.48-0.60, SL 0.40-0.50, ML 0.83-1.02, PL 0.20-0.25, CI 84-92, SI 75-86.
(holotype and paratypes). Head in full-face view slightly longer than broad (CI 84-92), sides slightly convex, posterior margin slightly rounded to almost straight, and occipital corners broadly rounded; occipital margin bearing distinct carina. Antennal scape relatively long (SI 75-86), extending well beyond 2/3 of head length but not reaching posterolateral corner of head; antennal segments II-VIII each broader than long, antennal segments IX and X longer than broad; length of segments II-IX continuously rising; terminal segment (X) longer than VIII and IX taken together; last four segments forming indistinct club. Frontal carina long and distinct, surpassing posterior margin of antennal torulus. Clypeus very short, its anterior margin almost straight to feebly concave, with lateral portions bluntly angled. Masticatory margin of mandible with large acute apical tooth, followed by medium-sized subapical tooth, 4 (rarely 3) small denticles, and medium-sized basal tooth; denticles and basal tooth worn out and hard to see in few paratypes; basal margin straight, lacking denticles. Gap between closed mandibles and anterior clypeal margin relatively small, about 0.5-0.6 times as broad as maximum width of mandible. With mesosoma in profile, promesonotum strongly convex, sloping gradually to the weakly developed but distinct metanotal groove; mesopleuron relatively short, demarcated from metapleuron by distinct groove; metapleural gland bulla moderately large, its maximum diameter about 1.3 times as long as distance between propodeal spiracle and most proximate part of metapleural gland bulla. Dorsal outline of propodeum in profile weakly convex, gently sloping posteriorly; propodeal junction angulated, overhanging declivity of propodeum, which is shallowly concave and encircled with thin but distinct rim. Petiole excluding subpetiolar process in profile slightly higher than long; petiolar node with steep anterior face and broadly convex dorsal outline; subpetiolar process developed, its ventral outline trapezoidal and rectangular, its apex on anterior part of process; ventralmost part of subpetiolar process with thin almost transparent lamellae. Postpetiole slightly shorter than petiole, in profile dorsal outline of node convex with small entirely flat area on dorsum; postpetiolar process developed, angulate, pointing anteriorly.
Head entirely smooth and shiny except for finely punctate antennal torulus. Mandible finely striate. Antennal scape entirely punctate. Mesosoma entirely finely reticulate with exception of pronotum and metapleuron; pronotum finely reticulate with large smooth and shiny median area on sides and dorsum; in few larger paratypes pronotal dorsum very finely and superficially reticulate but still smooth and shiny; anterior part of metapleuron smooth and shiny (with very fine and superficial longitudinal rugae in few larger paratypes). Entire petiole, including subpetiolar process, finely reticulate. Postpetiole finely reticulate, with flat surface on dorsum smooth and shiny. Gaster entirely smooth and shiny. Legs weakly punctate, more strongly so on tibiae, coxae smooth and shiny.
Body except sides of mesosoma with abundant standing and decumbent hairs of variable length; length of longest hairs on dorsum of head and pronotum 0.15–0.20 mm. Antennal scapes and legs with abundant decumbent hairs. Antennae, mesosoma, petiole and postpetiole reddish to yellowish brown, gaster and legs yellowish brown.
Male and female are unknown.
Aenictus hoelldobleri sp. n. (CASENT0914932). A Head in full face view B Body in profile C Body in dorsal view. All images are from http://www.antweb.org (photographer: Michele Esposito).
The species epithet is a patronym in honor of the great German myrmecologist Berthold ‘Bert’ Hölldobler and his invaluable and outstanding contributions to our understanding of ant societies.
eight workers in total; two from CHINA, Zhejiang Province, Gutianshan National Nature Reserve, ca. 30 km NW of Kaihua, 29°12'2"N / 118°7'54"E, 345 m asl, 29.V.2009, pitfall trap, leg. Andreas Schuldt, label: “CSP25/NE4(2009)” (IZAS); one with same data except label “CSP25/SW4(2009)” (CASC: CASENT0914930); one with same data except 14.VI.2009, label “CSP25/NE5(2009)” (IZAS); one with same data except 29°12'53"N / 118°8'5"E, 366 m asl, label “CSP24/NW4(2009)” (IZAS); one with same data except 29°12'53"N / 118°8'5"E, 366 m asl, label “CSP24/SW4(2009)” (CASC: CASENT0914929); one with same data except 29°14'58"N / 118°7'19"E, 620 m asl, 26.VI.2009, label “CSP12/NE6(2009)” (ZMBH); one with same data except 29°14'47"N / 118°6'58"E, 402 m asl, 29.VIII.2009, label “CSP13/NW10(2009)” (IZAS).
South-east China, provinces Zhejiang and Jiangxi (Fig.
The species is so far known to inhabit secondary mixed evergreen broad-leaved forests at mid elevations (ca. 300-620 m) where it occurs from young to old successional stages (referred to as “Aenictus (ceylonicus group) sp. CN02” in
Aenictus hoelldobleri is most similar to A. henanensis Li & Wang, 2005 and A. wudangshanensis, two species that also inhabit subtropical broad-leaved forests in China. Aenictus hoelldobleri can easily be distinguished from both species by the shape of the subpetiolar process, which is weakly developed and rounded in A. henanensis (characters for A. hoelldobleri are given in brackets: rectangular- trapezoidal, with a thin lamellae on the ventral outline) and rectangular with a very acute median apex that faces downwards in A. wudangshanensis. Furthermore, A. henanensis has the dorsum of the petiolar node smooth and shiny (finely reticulate) and lacks long, standing hairs on the dorsum of the head (longest hairs 0.15-0.20 mm). Aenictus wudangshanensis also has the mandible in total with 9 teeth/denticles (6-7). The three afore discussed species share with A. thailandianus, A. lifuiae Terayama, 1984, and A. yangi Liu, Hita Garcia, Peng & Economo, 2015 the mandible with six or more teeth/denticles and the relatively small gap between the closed mandibles and the anterior clypeal margin. Aenictus hoelldobleri can be separated from A. thailandianus by the sculpture of the dorsa of promesonotum and postpetiole, which are in A. thailandianus entirely punctate and not shiny (smooth and shiny, at most very finely and superficially reticulate but still smooth and shiny). Aenictus lifuiae and A. yangi differ from A. hoelldobleri by having the dorsum of the mesonotum and the dorsum of the petiole entirely smooth and shiny (finely reticulate). Furthermore, the legs of A. lifuiae are smooth and shiny (legs weakly punctate, most strongly on tibiae, coxae smooth and shiny) and the dentition of the mandible differs by having a large acute apical tooth followed by a series of 6-7 denticles of two sizes, the larger alternating with 1-2 smaller (large acute apical tooth, followed by a medium-sized subapical tooth, 3-4 minute denticles and a medium-sized basal tooth). The dentition of the mandible can also be used to separate A. hoelldobleri from A. yangi, in which the large acute apical tooth is followed by the medium-sized subapical tooth, one denticle, one medium sized tooth, two denticles, and the medium-sized basal tooth. Also, the maximum width of the gap between the anterior clypeal margin and the closed mandibles is in A. yangi at least about as broad as the maximum width of the mandibles (gap clearly smaller than maximum width of mandible).
Four workers from CHINA, Zhejiang Province, Gutianshan National Nature Reserve, ca. 30 km NW of Kaihua, 29°14'28"N / 118°6'37"E, 413 m asl, 30.VII.2008, pitfall trap in secondary mixed evergreen broad-leaved forest, leg. Andreas Schuldt, label: “CSP8/SE” (1 each in CASC: CASENT0914928 and IZAS).
Taiwan, Zhejiang (Fig.
This is the first record of A. formosensis from the Chinese mainland. Aenictus formosensis has been described and illustrated in detail by
Seven workers from CHINA, Jiangxi Province, near the village Xingangshan, ca. 15 km SE of Wuyuan, 29°5'21"N / 117°55'43"E, 136 m asl, 29.V.2013, hand collection on ground in an early successional tree plantation, leg. Michael Staab, label “MS1422” (1 each in CASC: CASENT0914926, IZAS, and ZMBH).
Guangxi, Hong Kong, Jiangxi (Fig.
Aenictus fuchuanesis has been described and illustrated in detail by
Three workers from CHINA, Guizhou Province, Leigongshan, 6.VII.1988, leg. Minsheng Wang; original label in Chinese “贵州雷公山 / 1988.VII.6 /王敏生 /中科院动物所“; (in IZAS: IOZ(E)1379709, all three workers on a single pin).
Guizhou, Yunnan (Fig.
The three specimens of A. thailandianus from Leigong Moutain, Guizhou Province, agree well with the original description of
Three workers from CHINA, Guizhou Province, Leigongshan, 6.VII.1988, leg. Minsheng Wang; original label in Chinese “贵州雷公山 / 1988.VII.6 /王敏生 /中科院动物所“; (in IZAS: IOZ(E)1379710, all three workers on a single pin).
Guizhou (Fig.
The three specimens of A. watanasiti from Leigong Moutain, Guizhou Province, agree very well with the original description and the illustrations of
Four workers from CHINA, Zhejiang Province, Gutianshan National Nature Reserve, ca. 30 km NW of Kaihua, 29°15'18"N / 118°8'51"E, 880 m asl, 25.VI.2009, pitfall trap in secondary mixed evergreen broad-leaved forest, leg. Andreas Schuldt, label: “CSP6/SE6(2009)” (1 each in CASC: CASENT0914927 and IZAS).
Hubei, Zhejiang (Fig.
So far A. wudangshanensis has been known only from the type series collected in the Wudangshan Nature Reserve, Hubei Province. The four specimens from the Gutianshan National Nature Reserve agree very well with the original description of
The genus Aenictus with its type-species A. ambiguus Shuckard, 1840 was originally established and described based on the male caste. In the Chinese Aenictus fauna there are eight species and subspecies only known from males (
Most Aenictus species are largely restricted to forests. Unfortunately, forests in China and elsewhere in Asia have been and are still continuously cleared and transformed into agriculture or tree plantations (e.g.
There are many records of A. ceylonicus from south and east China (listed in
The diversity center for the A. ceylonicus group seems to be in continental South-East Asia (
I thank the administration of the Gutianshan National Nature Reserve for granting research permissions for the forests under their management and Andreas Schuldt for collecting material. Hong Liu and Jun Chen generously allowed me to work in the Insect Collection of the Institute of Zoology, Chinese Academy of Sciences, in Beijing and loaned specimens. I also thank Chao-Dong Zhu and Huan-Xi Cao for organizing my stay in Beijing and Ying Li for help with translations. Brian Fisher and Michele Esposito kindly provided automontage images, and Francisco Hita Garcia gave constructive comments on an earlier version of the manuscript. Funding by the German Research Foundation (DFG FOR 891, 891/2, KL 1849/6-1) is gratefully acknowledged. The article processing charge was funded by the German Research Foundation (DFG) and the Albert-Ludwigs-University Freiburg in the funding program Open Access Publishing.