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A sibling species of Aenictus dentatus FOREL, 1911 (Hymenoptera: Formicidae) from continental Southeast Asia

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  • Natural History Museum of the National Science Museum, Thailand

Abstract and Figures

A new species of army ant, closely related to Aenictus dentatus FOREL, 1911, is described and illustrated based on the worker caste under the name Aenictus paradentatus JAITRONG & YAMANE sp.n. This species is distributed in the conti-nental Southeast Asia, while A. dentatus is restricted to Sundaland. Introduction "Aenictus dentatus FOREL, 1911" has been recorded from a wide range of tropical Asia including India, southern-most part of China and various countries. We have ex-amined a rich material of "A. dentatus" collected from Southeast Asia and compared them with syntypes of A. dentatus from Malacca, Peninsular Malaysia. After a care-ful study we have reached the conclusion that A. dentatus is restricted to Sundaland (southern part of Malay Peninsula, Sumatra, Borneo, and Java) and that the populations of con-tinental Southeast Asia (Vietnam, Laos and Thailand) be-long to a closely related but distinct biological species. Both share the distinctive coarse sculpture on the head and meso-soma, and the relatively long antennal scape, extending bey-ond the posterior margin of the head. However, they dif-fer in some characters (shape of head, scape length, shape of petiole and sculpture on mesosoma and gaster), and dis-tribution pattern. In the present paper we describe this unidentified spe-cies as a new species based on the worker caste. Aenictus dentatus is also redescribed based on the lectotype and para-lectotypes, which are designated below. The distributions of both species are discussed. Methods Most morphological observations were made with a Nikon SMZ1000 stereoscope. Multi-focused montage images were produced using Helicon Focus 4.75 Pro from a series of
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Myrmecological News 16 133-138 Vienna, January 2012
A sibling species of Aenictus dentatus FOREL, 1911 (Hymenoptera: Formicidae) from
continental Southeast Asia
Weeyawat JAITRONG, Seiki YAMANE & Wattanachai TASEN
Abstract
A new species of army ant, closely related to Aenictus dentatus FOREL, 1911, is described and illustrated based on the
worker caste under the name Aenictus paradentatus JAITRONG & YAMANE sp.n. This species is distributed in the conti-
nental Southeast Asia, while A. dentatus is restricted to Sundaland.
Key words: Taxonomy, Formicidae, Aenictinae, Aenictus paradentatus, army ant, new species.
Myrmecol. News 16: 133-138
ISSN 1994-4136 (print), ISSN 1997-3500 (online)
Received 10 December 2010; revision received 4 February 2011; accepted 20 February 2011
Subject Editor: Herbert Zettel
Weeyawat Jaitrong, Department of Natural Sciences, Graduate School of Science and Engineering, Kagoshima Uni-
versity, Kagoshima, Japan; Natural History Museum, National Science Museum, Technopolis, Khlong 5, Khlong Luang,
Pathum Thani, 12120 Thailand. E-mail: polyrhachis@yahoo.com
Seiki Yamane, Dept. Natural Sciences, Graduate School of Science and Engineering, Kagoshima Univ., Kagoshima, Japan.
Wattanachai Tasen (contact author), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok,
10900 Thailand. E-mail: fforwct@ku.ac.th
Introduction
"Aenictus dentatus FOREL, 1911" has been recorded from
a wide range of tropical Asia including India, southern-
most part of China and various countries of Southeast Asia
(WILSON 1964, TERAYAMA & YAMANE 1989, TERAYAMA
& KUBOTA 1993, XU 1994, BOLTON 1995, ZHOU & CHEN
1999, ITO & al. 2001, ZHOU 2001, ANNETTE & al. 2003,
YAMANE & al. 2003, EGUCHI & al. 2005, JAITRONG &
NABHITABHATA 2005, BOLTON & al. 2007). We have ex-
amined a rich material of "A. dentatus" collected from
Southeast Asia and compared them with syntypes of A.
dentatus from Malacca, Peninsular Malaysia. After a care-
ful study we have reached the conclusion that A. dentatus is
restricted to Sundaland (southern part of Malay Peninsula,
Sumatra, Borneo, and Java) and that the populations of con-
tinental Southeast Asia (Vietnam, Laos and Thailand) be-
long to a closely related but distinct biological species. Both
share the distinctive coarse sculpture on the head and meso-
soma, and the relatively long antennal scape, extending bey-
ond the posterior margin of the head. However, they dif-
fer in some characters (shape of head, scape length, shape
of petiole and sculpture on mesosoma and gaster), and dis-
tribution pattern.
In the present paper we describe this unidentified spe-
cies as a new species based on the worker caste. Aenictus
dentatus is also redescribed based on the lectotype and para-
lectotypes, which are designated below. The distributions
of both species are discussed.
Methods
Most morphological observations were made with a Nikon
SMZ1000 stereoscope. Multi-focused montage images were
produced using Helicon Focus 4.75 Pro from a series of
source images taken by a Nikon EOS Kiss X4 digital cam-
era attached to a Nikon ECLIPSE E600 microscope. Wor-
kers of each species were measured using a micrometer
(accurate to 0.01 mm).
The abbreviations used for the measurements and in-
dices are as follows:
CI Cephalic index, HW / HL × 100.
HL Maximum head length in full-face view, measured
from anterior clypeal margin to midpoint of a line
drawn across posterior margin of head.
HW Maximum head width in full-face view.
ML Mesosomal length measured in profile from the point
at which the pronotum meets the cervical shield to
the posterior margin of propodeal lobe.
PL Petiole length measured from anterior margin of ped-
uncle to posteriormost point of tergite.
SI Scape index, SL / HW × 100.
SL Scape length excluding basal constriction and con-
dylar bulb.
TL Total length, roughly measured from anterior mar-
gin of head to tip of gaster in stretched specimens.
Abbreviations of the type depositories are as follows:
BMNH The Natural History Museum, London, UK
MCZC Museum of Comparative Zoology, Cambridge,
MA, USA
MHNG Muséum d'Histoire Naturelle, Geneva, Switzer-
land
SKYC Collection of Sk. Yamane at Kagoshima Univer-
sity, Japan
THNHM Natural History Museum of the National Science
Museum, Thailand
Figs. 1 - 4: Aenictus dentatus. (1) Habitus, lateral aspect, lectotype. (2) Head, full-face view, lectotype. (3) Sculpture on
first gastral tergite. (4) Habitus, dorsal aspect.
Systematics
Aenictus dentatus FOREL, 1911 (Figs. 1 - 5, 11 - 12)
Aenictus aitkeni var. dentatus FOREL, 1911: 383.
Aenictus dentatus: WILSON 1964: 460; BOLTON 1995: 59.
Types. Aenictus aitkeni var. dentatus: six syntype workers
(two pins, three on each pin) from Berhentian Tingi, Ma-
lacca, Malaya (MHNG, examined). One worker (top on a
pin) is designated here as the lectotype, the others as para-
lectotypes.
Non-type material examined. Thailand: Narathi-
wat Prov., Bala-Hala W.S., tropical rain forest, 26.IX.
2001, leg. C. Bourmas (SKYC, THNHM). M a l a y s i a :
Malay Peninsula, Selangor Prov., Ulu Gombak ca. 250 m
a.s.l., 19.X.1999, VW-06, leg. V. Witte (SKYC, THNHM);
Sabah, Poring, Kinabalu, 800 m a.s.l., 17.III.1995, leg. T.
Kikuta (SKYC); Sabah, Sepilok Forest, 25.I.1997, Eg96-
BOR-475, leg. K. Eguchi, (SKYC, THNHM); Sabah, Sepi-
lok Forest, 27.VIII.1995, leg. Sk. Yamane (SKYC); Sabah,
Tawau Hills N.P., 11.VII.1996, SB96-SKY-27, leg. Sk.
Yamane (SKYC, THNHM); Sabah, Gunong Rara, Tawau
Hills N.P., 10.XII.1996, Eg96-BOR-333, leg. K. Eguchi,
(SKYC); Sabah, Mahua, Tambunan, 2.VI.2005, leg. Bakh-
tiar (SKYC); Sabah, Sepilok, 29.V.2005, leg. Bakhtiar
(SKYC); Sarawak, Miri, Lambir N.P., Bt. Lambir, 12.I.1993,
leg. Sk. Yamane (SKYC, THNHM); Sarawak, Miri, Lam-
bir N.P., 13.VIII.1995, leg. Sk. Yamane (SKYC, THNHM);
same loc., 30.VI.2004, leg. Sk. Yamane (SKYC, THNHM);
same loc., 2.I.1998, leg. Sk. Yamane (SKYC, THNHM);
same loc., 19.IV.1993, leg. Sk. Yamane (SKYC, THNHM).
r u n e i : Tasek Merimbun, 12.II.1999, Eg99-BOR-060, B
Fig. 5: Aenictus dentatus, petiole and postpetiole, lateral
aspect, lectotype.
leg. K. Eguchi, (SKYC, THNHM). I n donesia: E. Kali-
mantan, Kutai N.P., 7.VIII.1992, leg. Sk. Yamane (SKYC);
W. Sumatra, Lubuk Gadang, 21 - 23.VIII.1985, leg. Sk.
Yamane (SKYC); W. Sumatra, Padang, Ulu Gadut, Bt.
Lantik, 450 m a.s.l., 19.I.1988, leg. M. Kato (SKYC); S.
Sumatra, Lampung Barat, Bodong Jaya, Sumberjaya, 18.IX.
2007, SU07-SKY-197, leg. Sk. Yamane (SKYC, THNHM);
W. Java, Pangandaran, 15.XII.1995, FI95-676, leg. F. Ito
(SKYC, THNHM).
Redescription of workers. Measurements of lectotype.
TL 4.55 mm; HL 1.00 mm; HW 0.78 mm; SL 1.15 mm;
ML 1.50 mm; PL 0.35 mm, CI 78; SI 148.
Measurements of paralectotypes (n = 5). TL 4.40 -
4.45 mm; HL 0.95 - 1.00 mm; HW 0.72 - 0.78 mm; SL
1.08 - 1.13 mm; ML 1.45 - 1.50 mm; PL 0.33 - 0.35 mm,
CI 76 - 79; SI 143 - 152.
Head in full-face view oval, distinctly longer than broad,
with distinctly convex sides; posterior margin strongly con-
vex; occipital margin bearing a distinct collar. Antenna
134
Figs. 6 - 9: Aenictus paradentatus sp.n. (6) Habitus, lateral aspect, holotype. (7) Head, full-face view, holotype. (8) Sculp-
ture of first gastral tergite, holotype. (9) Habitus, dorsal aspect.
10-segmented; scape very long, much extending beyond
posterolateral corner of head; all funicular segments lon-
ger than broad; apical segment almost as long as three
previous ones. Frontal carinae well developed, fused at the
level of antennal base to form a single carina, extending
less than half length of head, very poorly developed in
posterior half. Parafrontal ridge well developed, extend-
ing of head length; seen in profile, its anteriormost
part well developed and subtriangular. Clypeus short and
roundly produced anteriorly, lacking anterior denticles.
Mandible triangular, its masticatory margin with large api-
cal tooth, followed by 15 denticles; basal margin of man-
dible lacking denticles. Mesosoma elongate and stout; pro-
mesonotum (seen in profile) with slightly convex dorsum,
sloping gradually to metanotal groove; propodeum lower,
with feebly convex dorsum; propodeal junction developed
into a high, thin transverse ridge, which in profile appears
as a large, acute tooth overhanging declivity of propodeum.
Petiole with short but distinct peduncle; node short and
posteriorly elevated, in profile with anterior and dorsal
surfaces continuous, posterior slope steep; subpetiolar pro-
cess weakly developed and subtriangular, its apex directed
downward. Postpetiole almost as long as petiole, its dor-
sal surface convex. Gaster elliptical, narrowed anteriorly
and posteriorly.
Head, mesosoma, petiole and postpetiole entirely micro-
punctated and opaque. In addition, promesonotum dorsally
rugose, and laterally with five to six longitudinal rugae;
propodeum dorsally with three to four longitudinal cari-
nae; petiole in dorsal view with longitudinal or irregular
rugae. First gastral tergite and sternite smooth and shiny,
except for the basalmost part with dense micropunctures.
Head and mesosoma with relatively dense standing
hairs; length of the longest pronotal hairs 0.38 - 0.40 mm.
Head and mesosoma dark reddish brown; antenna, legs,
waist and gaster reddish brown or yellowish brown. Typh-
latta spot absent.
Distribution. Southernmost part of Thailand, Penin-
sular Malaysia, Sumatra, Borneo (Sabah, Brunei, Sarawak,
and East Kalimantan), and Java (Fig. 11).
Remarks. In several characters variation is found that
may or may not be of geographic nature. The subpetiolar
process varies from low (its ventral outline weakly con-
vex as seen in the Sumatran population and some colonies
collected from Borneo such as Eg96-BOR-475, SB96-SKY-
26 and SR04-SKY-11) to subtriangular (apex directed down-
ward as seen in the type series and some colonies collected
from Borneo such as Eg96-BOR-324 and Eg-BOR-545,
and the single colony collected by Sk. Yamane from East
Kalimantan). Size variation occurs between populations; the
specimens from Sumatra are slightly larger than the type
series (HW 0.80 - 0.85 mm vs. 0.72 - 0.78 mm). Within the
Bornean population the variation in head width is greater:
0.75 mm to 0.88 mm. The specimens collected from Bor-
neo tend to be darker in coloration than the lectotype and
the other specimens from Malay Peninsula. However, in
most of the characters the specimens from all parts of Sunda-
and agree with the type series, except for the single colony l
135
Fig. 10: Aenictus paradentatus sp.n., petiole and postpeti-
ole, lateral aspect, holotype.
collected from West Java (FI95-676, SKYC and THNHM),
in which the propodeal junction is simply right-angled, in
profile not forming a overhanging tooth. We regard this
difference as an intraspecific variation.
Bionomics. According to ANNETTE & al. (2003) in Pa-
soh, Malay Peninsula, Aenictus dentatus foraged on the
forest floor in the day and night and preyed on ants of the
genus Pheidole WESTWOOD, 1839. We found this species
preying on the ants of the genus Nylanderia EMERY, 1906 in
Lambir National Park, Sarawak (SR04-SKY-11). This spe-
cies occurs from the sea level to highlands (up to 1,300 m
a.s.l., Bodong Jaya, southern Sumatra) and inhabits prim-
ary and disturbed forests.
Aenictus paradentatus JAITRONG & YAMANE sp.n.
(Figs. 6 - 12)
Etymology. The specific epithet paradentatus is a com-
pound word meaning "similar to dentatus".
Types. Holotype: worker from Doi Suthep-Pui National
Park, Muang Dist., Chiang Mai Prov., N. Thailand, 20.
VIII.1998, W. Jaitrong leg., WJT98-PD01 (THNHM). Para-
types: 17 workers, same data as holotype (BMNH, MCZC,
MHNG, SKYC, THNHM).
Non-type materials examined. V i e tn a m : Ninh Binh
Prov., Nho Quan Dist., Cuc Phuong N.P., 11.VIII.1998,
VN98-HO-026, leg. H. Okido (SKYC, THNHM); same
loc., 9.XI.2001, VN01-SKY-40, leg. Sk. Yamane (SKYC);
Bac Giang, Tay Yen, 150 m a.s.l., 29. - 31.V.2004, Eg04-
VN-146, leg. K. Eguchi (SKYC); Quang Ninh, Chua Yen
Tu, 520 - 725 m a.s.l., 18.V.2004, Eg04-VN-004, leg. K.
Eguchi (SKYC); Vinh Phuc Prov., Tam Dao N.P., 900 m
a.s.l., 7.VIII.1998, VN98-SKY-06, leg. Sk. Yamane (SKYC,
THNHM); Nghe An Prov., Pu Hoat, VI.1999, VN9902,
leg. T. V. Bui (SKYC, THNHM). L a o s : Vientiane, Na-
xaythong Dist., Sivilay Village, 10.VI.2010, WJT10-LAO12
= LA10-SKY-065, leg. W. Jaitrong, (SKYC, THNHM); Pak
Ngum Dist., Phang Dang Village, 12.VI.2010, WJT10-
LAO16 = LA10-SKY-126, leg. W. Jaitrong (SKYC,
THNHM); same loc., 14.VI.2010, WJT10-LAO16, leg. W.
Jaitrong (THNHM). T h a i l a n d : Chiang Mai Prov., Doi
Phahom Pok, 28.V.2008, WJT08-N33, leg. W. Jaitrong
(SKYC, THNHM); Chiang Mai Prov., Doi Ang Khang,
13.VII.2000, WJT00-TH061, leg. W. Jaitrong (SKYC,
THNHM); Chiang Mai Prov., Doi Chiang Dao, 500 - 600 m
a.s.l., 19.VIII.1998, TH98-SKY-09, leg. Sk. Yamane
(SKYC); Mae Hong Son Prov., Pang Mapha Dist., Tham
Lod, 6 III 2008, WJT08-TL01, leg. W. Jaitrong (SKYC,
THNHM); Uthai Thani Prov., Ban Rai Dist., Kan Ma
Kud Village, 18.VI.2010, HKK10-06-06, leg. W. Jaitrong
(THNHM); Chaiyaphum Prov., Phu Kheao, 13.I.1999,
WJT99-TH64, leg. W. Jaitrong (SKYC, THNHM); Loei
Prov., Phu Luang, 11.IV.2008, TH08-SKY-103, leg. Sk.
Yamane (SKYC, THNHM); Nakhon Ratchasima Prov., Sa-
khaerat ERS., 22.XI.1999, WJT99-TH46, leg. W. Jaitrong
(SKYC, THNHM); Chachoengsao Prov., Khao Ang Reu
Nai, 21.VIII.2003, TH03-SKY-43, leg. Sk. Yamane (SKYC,
THNHM); Chanthaburi Prov., Pheao, 22.XI.2003, TH03-
HS12, leg. S. Hasin (SKYC, THNHM); Prachuap Kirikhan
Prov., Tabsakae Dist., 5.VIII.2009, WJT09-TH2002, leg.
W. Jaitrong (SKYC, THNHM).
Worker description (holotype and paratypes). Mea-
surements of holotype: TL 4.65 mm; HL 1.03 mm; HW
0.90 mm; SL 1.08 mm; ML 1.53 mm; PL 0.33 mm; CI
88; SI 119.
Measurements of paratypes (n = 9): TL 4.55 - 4.65 mm;
HL 0.95 - 1.05 mm; HW 0.80 - 0.93 mm; SL 0.93 - 1.08 mm;
ML 1.50 - 1.55 mm; PL 0.33 - 0.35 mm; CI 83 - 88; SI
117 - 124.
Head in full-face view round, slightly longer than broad,
with convex sides and posterior margin; occipital carina
bearing distinct collar. Antenna 10-segmented; scape long,
extending beyond posterolateral corner of head; funicular
segment I almost as long as II, but slightly shorter than
III - VI; apical segment almost as long as three previous
ones. Frontal carinae well developed, fused at level of an-
tennal base to form a single carina, extending less than
half length of head, very poorly developed in posterior half.
Parafrontal ridge well developed, extending of head
length; seen in profile, its anteriormost part well devel-
oped and subtriangular. Clypeus short and roundly pro-
duced anteriorly, lacking anterior denticles. Mandible tri-
angular, its masticatory margin with large apical tooth, fol-
lowed by 11 - 12 denticles; basal margin of mandible
lacking denticles. Mesosoma rather elongate and stout; pro-
mesonotum in profile with strongly convex dorsum, slop-
ing gradually to metanotal groove; propodeum lower and
with almost straight dorsum; mesopleuron not demarcated
from metapleuron; propodeal junction acutely angulated,
protruding as ridge that is often slightly upward directed;
declivity of propodeum shallowly concave, encircled with
very narrow rim. Petiole almost as long as high without
peduncle, its dorsal outline elevated posteriorly; subpetiolar
process generally very low, its ventral outline weakly con-
vex. Postpetiole seen in profile slightly larger than petiole,
its dorsal outline elevated posteriorly. Gaster elliptical, nar-
rowed anteriorly and posteriorly.
Head, mesosoma, petiole and postpetiole entirely and
densely micropunctate and opaque. In addition, promeso-
notum dorsally rugose, laterally with approximately ten
longitudinal rugae; dorsal petiolar surface with longitudi-
nal or irregular rugae. First gastral segment very weakly
shagreened with smooth and shiny interspaces, except in
basalmost part with dense micropunctures.
Head and mesosoma with relatively dense standing hairs;
length of longest pronotal hairs 0.43 - 0.45 mm. Entire
body dark reddish brown or dark brown. Typhlatta spot ab-
sent.
Distribution. Vietnam, Laos, and Thailand (Fig. 11).
Remarks. The specimens from the distribution range
(Vietnam, Laos, and Thailand) agree in most characters
well with the type series from Doi Suthep-Pui National
Park, northern Thailand. Size variation occurs in the wor-
ker (HW: 0.75 - 0.95 mm). For example, in the single col-
ony collected from Laos (WJT10-LAO16) the head width
136
is much smaller than in the type series and the others (HW:
0.75 - 0.78 mm in the former, and 0.80 - 0.93 mm in the
type series). In most specimens the subpetiolar process is
very low with its ventral outline weakly convex as seen
in the type series, but in two specimens collected from
Doi Ang Khang (ca. 1,300 m a.s.l.), northern Thailand it
is more developed, protruded anteroventrally.
Bionomics. Aenictus paradentatus occurs from low-
lands to highlands (up to 1,300 m a.s.l., Doi Ang Khang,
N. Thailand) and inhabits primary and disturbed forests
(rarely marching even in grasslands in the mountain range
of N. Vietnam). We observed this species preying on other
ants such as species of Leptogenys R
OGER, 1861 (Viet-
nam, VN98-SKY-15), Oecophylla SMITH, 1860 (Thailand,
HKK10-06-06), Pachycondyla SMITH, 1858 (Laos, WJT10-
LAO16) and Pheidole (Vietnam, VN98-SKY-15), and also
on termites, Macrotermes sp. (Laos, WJT10-LAO12).
Discussion
Aenictus paradentatus sp.n. and A. dentatus are very simi-
lar in general appearance as they share the distinctive coarse
sculpture on head and mesosoma, and the relatively long
antennal scape, extending beyond the posterior margin of
the head. However, they differ in several significant cha-
racters. The antennal scape is relatively shorter in A. para-
dentatus (SI 117 - 124) than in A. dentatus (SI 143-152).
Figure 12 shows the ratio of HW / SL in the workers of
A. dentatus (34 specimens) and A. paradentatus (47) from
throughout their distribution ranges; no overlapping is ob-
served in HW / SL between the species. The posterior por-
tion of the head in full-face view is relatively broader in
A. paradentatus (Fig. 7) than in A. dentatus (Fig. 2). The
first gastral tergite is weakly shagreened with smooth in-
terspaces in the former (Fig. 8), while it is wholly smooth
and shiny in the latter (Fig. 3). The petiole has no ped-
uncle in the former, but has a short but distinct peduncle in
the latter.
The new species Aenictus paradentatus is distinctly al-
lopatric with A. dentatus in distribution. It occurs in con-
tinental Southeast Asia from the southern part of China
to the lowest latitude in Peninsular Thailand, ca. 200 km
north of the Isthmus of Kra. The distribution pattern of this
species, and also of A. artipus WILSON, 1964 (JAITRONG &
al. 2010), is rather similar to those of many bird and snake
species inhabiting this region (e.g., WOODRUFF 2003). On
the other hand, A. dentatus is confined to Sundaland (Ma-
lay Peninsula, Borneo, Sumatra, and Java); so far the north-
ernmost latitude of the range of this species is known at
the southernmost part of Thailand, Narathiwat Province
(Malay Peninsula, ca. 600 km south of the Isthmus of Kra).
This species is almost sympatric with the A. silvestrii WHEE-
LER, 1929 group (except for A. jarujini JAITRONG & YA-
MANE, 2010 found in northern Thailand) (JAITRONG &
NUR-ZATI 2010, JAITRONG & YAMANE 2010), and the
genus Cladomyrma WHEELER, 1920 (AGOSTI & al. 1999,
but see below).
There are known two phytogeographical transitions on
the Malay Peninsula: One is the southern transition be-
tween perhumid evergreen rainforest and wet seasonal ev-
ergreen rainforest, 400 - 500 km south of Isthmus of Kra
near the Thai-Malay border (VAN STEENIS 1950), and the
other is the northern transition between wet seasonal ever-
reen rainforest and mixed moist deciduous forest just g
Fig. 11: Distribution of Aenictus dentatus and A. paraden-
tatus sp.n.
Fig. 12: Scape length against head width in the worker.
north of the isthmus (RICHARDS 1996). According to the
collecting sites, Aenictus paradentatus is very probably re-
stricted to the seasonal forest (hill evergreen forest, dry
evergreen forest, mixed deciduous forest, grassland) lo-
cated northward from the Isthmus of Kra, in both primary
and disturbed conditions, while A. dentatus is a distinctly
Sundaic species inhabiting the perhumid evergreen rain-
forest (for vegetation types in this area, see GÖLTENBOTH
& ERDELEN 2006). So far no overlapping in the distribu-
tion of the two species has been recorded beyond north-
ern and southern phytogeographical transitions.
The pattern found in the ant genus Cladomyrma is
slightly different since at least two species are found in
patchy wet forests in Thailand and Vietnam (FUJIWARA &
al. 2004, EGUCHI & BUI 2006). The species of this genus
are associated with obligate host plants, some species be-
ing restricted to a single plant species or genus and some
others with several host plants (AGOSTI & al. 1999). Thus
the distributions of Cladomyrma species are dependent on
the distributions of their host plants. On the other hand, the
Aenictus species do not have any association with particu-
137
138
lar plant species, but probably with vegetation types. The
case of A. paradentatus and A. dentatus seems roughly to
coincide with that of bird species and bird communities
(cf. MACARTHUR & MACARTHUR 1961; HUGHES & al.
2003).
XU (1994), ZHOU & CHEN (1999), ZHOU (2001) re-
ported Aenictus dentatus from southern China, and TERA-
YAMA & KUBOTA (1993) from Khanh Hoa Province, Viet-
nam. However, as mentioned above, specimens of this
group collected from those areas most probably belong to
A. paradentatus. All Thai and Vietnamese Aenictus speci-
mens cited as A. dentatus in YAMANE & al. (2003), EGU-
CHI & al. (2005), JAITRONG & NABHITABHATA (2005) were
reidentified as A. paradentatus in the present study, except
for the single colony collected from the peninsula (Narathi-
wat Province) being the true A. dentatus. WILSON (1964)
cited Bombay [Mumbai], India, as a locality of A. denta-
tus, but the identification should be reconfirmed.
Acknowledgments
We would like to express our deep gratitude to Dr. Bern-
hard Merz (Muséum d'Histoire Naturelle Geneva, Switzer-
land), who loaned us the type material of A. aitkeni var.
dentatus. We are grateful to Dr. Kastuyuki Eguchi (Naga-
saki University), Prof. Fuminori Ito (Kagawa University),
Dr. Tuan Viet Bui (Institute of Ecological Resources), Mr.
Tuah Bin Atar (Brunei Museum), Dr. Bakhtiar Effendi
Yahya (Universiti Malaysia Sabah), Ms. Sasitorn Hasin
(Kasetsart University) and other friends for their help in
collecting specimens. Last but not least, we would like to
thank two anonymous reviewers and Editor Dr. H. Zettel
for their valuable and constructive comments on the manu-
script.
References
AGOSTI, D., MOOG, J. & MASCHWITZ, U. 1999: Revision of the
Oriental plant-ant genus Cladomyrma. American Museum
Novitates 3283: 1-24.
ANNETTE, K.F.M., ROSCISZEWSKI, K. & MASCHWITZ, U. 2003:
The ant species richness and diversity of a primary lowland rain
forest, the Pasoh Forest Reserve, West-Malaysia. In: OKUDA,
T., MANOKARAN, N., MATSUMOTO, Y., NIIYAMA, K., THOMAS,
S.C. & ASHTON, P.S. (Eds.): Pasoh: Ecology of a lowland rain-
forest in Southeast Asia. – Springer, Tokyo, pp. 348-373.
BOLTON, B. 1995: A new general catalogue of the ants of the
world. Harvard University Press, Cambridge, MA, 504 pp.
BOLTON, B., ALPERT, G., WARD, P.S. & NASKRECKI, P. 2007:
Bolton's catalogue of ants of the world, 1758-2005 [CD-ROM].
Harvard University, Cambridge, MA.
EGUCHI, K. & BUI, T.V. 2006: Cladomyrma scopulosa new spe-
cies (Hymenoptera: Formicidae) from Vietnam. – Sociobiol-
ogy 47: 305-314.
EGUCHI, K., BUI, T.V., YAMANE, Sk., OKIDO, H. & OGATA, K.
2005: Ant faunas of Ba Vi and Tam Dao, North Vietnam (In-
secta: Hymenoptera: Formicidae). – Bulletin of Institute of Trop-
ical Agriculture Kyushu University 27 (2004): 77-98.
FOREL, A. 1911: Fourmis nouvelles ou intéressantes. Bulletin
de la Société Vaudoise des Sciences Naturelles 47: 331-400.
FUJIWARA, N., MURASE, K., YAMAOKA, R., WIWATWITAYA, D.,
JAITRONG, W. & YAMANE, Sk. 2004: A comparison of compo-
sition and profile of surface chemicals between Cladomyrma
ants and their host plant Sphenodesme sp. ANeT Newsletter
7: 9-13.
GÖLTENBOTH, F. & ERDELEN, W. 2006: Climate. In: GÖLTENBOTH,
F., TIMOTIUS, K.H., MILAN, P.P. & MARGRAF, J. (Eds.): Ecol-
ogy of Insular Southeast Asia: The Indonesian Archipelago.
Leyte State University, Visca, Baybay, Leyte, pp. 17-26.
HUGHES, J.B., ROUND, P.D. & WOODRUFF, D.S. 2003: The Indo-
chinese-Sundaic faunal transition at the Isthmus of Kra: an
analysis of resident forest bird species distributions. – Journal
of Biogeography 30: 569-580.
ITO, F., YAMANE, Sk., EGUSHI, K., NOERDJITO, W.A., KAHONO S.,
TSUJI, K., OKAWARA, K., YAMAUCHI, K., NISHIDA, T., NAKA-
MURA, K. 2001: Ant species diversity in the Bogor Botanic
Garden, West Java, Indonesia, with descriptions of two new
species of the genus Leptanilla (Hymenoptera, Formicidae).
Tropics 10: 379-404.
JAITRONG, W. & NABHITABHATA, J. 2005: A list of known ant
species of Thailand (Hymenoptera: Formicidae). The Thai-
land Natural History Museum Journal 1: 9-54.
JAITRONG, W. & NUR-ZATI, A.M. 2010: A new species of the
ant genus Aenictus (Hymenoptera: Formicidae: Aenictinae) from
the Malay Peninsula. – Sociobiology 56: 449-454.
JAITRONG, W. & YAMANE, Sk. 2010: The army ant Aenictus sil-
vestrii and its related species in Southeast Asia, with a descrip-
tion of a new species (Hymenoptera: Formicidae: Aenictinae).
– Entomological Science 13: 328-333.
JAITRONG, W., YAMANE, Sk. & WIWATWITAYA, D. 2010: The army
ant Aenictus wroughtonii (Hymenoptera: Formicidae: Aenic-
tinae) and related species in the Oriental Region, with de-
scriptions of two new species. – Japanese Journal of Systematic
Entomology 16: 33-46.
MACARTHUR, R.H. & MACARTHUR, J.W. 1961: On bird species
diversity. Ecology 42: 594-598.
RICHARDS, P.W. 1996: The tropical rain forest: an ecological
study, 2nd edn. Cambridge University Press, Cambridge, UK,
262 pp.
TERAYAMA, M. & KUBOTA, A. 1993: The army ant genus Aenic-
tus (Hymenoptera: Formicidae) from Thailand and Viet Nam,
with descriptions of three new species. Bulletin of the Bio-
geographical Society of Japan 48: 68-72.
TERAYAMA, M. & YAMANE, Sk. 1989: The army ant genus Aenic-
tus (Hymenoptera, Formicidae) from Sumatra, with descrip-
tions of three new species. Japanese Journal of Entomology
57: 597-603.
VAN STEENIS, C.G.G.J. 1950: The delimitation of Malesia and
its main plants geographical divisions. Flora Malesiana Ser-
ies 1(1): LXX-LXXV.
WILSON, E.O. 1964: The true army ants of the Indo-Australian
area (Hymenoptera: Formicidae: Dorylinae). Pacific Insects
6: 427-483.
WOODRUFF, D.S. 2003: The location of the Indochinese-Sundaic
biogeographic transition in plants and birds. – Natural History
Bulletin of the Siam Society 51: 97-108.
XU, Z. 1994: A taxonomic study of the ant subfamily Dorylinae
in China (Hymenoptera Formicidae). – Journal of Southwest
Forestry College 14: 116-122.
YAMANE, Sk., BUI, T.V., OGATA, K., OKIDO, H. & EGUCHI, K.
2003: Ant fauna of Cuc Phuong National Park, North Vietnam
(Hymenoptera: Formicidae). – Bulletin of Institute of Tropical
Agriculture Kyushu University 25: 51-62.
ZHOU, S. 2001: Ants of Guangxi. Guangxi Normal University,
Guilin, 253 pp.
ZHOU, S. & CHEN, Z. 1999: The ant genus Aenictus SHUCKARD
from Guangxi (Hymenoptera: Formicidae). Guangxi Science
6: 63-64.
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