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Kasetsart J. (Nat. Sci.) 46 : 408 - 417 (2012)
Faculty of Science and Technology, Pibulsongkram Rajabhat University, Phitsanulok 65000, Thailand.
E-mail: g4761008@hotmail.com
Received date : 17/01/12 Accepted date : 02/03/12
INTRODUCTION
Webspinners or embiids belong to
the order Embiidina (Embioptera), a poorly
characterized and often overlooked insect order
with approximately 360 known species (Engel and
Grimaldi, 2006; Szumik et al., 2008). However,
Ross (2000a) speculated that the true number
was probably nearer to 2,000 species worldwide.
Typically, a few species live on remote islands,
but some species have spread to several continents
through anthropogenic intervention, especially
through transport as a result of overseas trade
(Ross, 2007). In particular, the genus Oligotoma,
Westwood, 1837 (Oligotomidae), has expanded
extensively by such anthropogenic-assisted
colonization (Ross, 2000a, 2007). Oligotomids
are readily recognized by their enlarged front tarsi,
which contain about a hundred silk glands that are
used for silk secretion (Nagashima et al., 1991;
Ross, 1955, 2000a) to spin a network of narrow
hollow tubes, or galleries.
Because most species are very
inconspicuous, spending most of their lives in
silk galleries, webspinners are somewhat rarely
observed by humans compared to the majority
of the more conspicuous insects (Poolprasert and
Edgerly, 2011), whilst they cause no economic
or known ecological impact upon humans,
because they feed on dead plant materials (Ross,
1991, 2007), removing much interest in them.
Nonetheless, they are very interesting insects with
a unique social behavior and ecology, and also
have some primitive morphological characteristics
and evolutionary biology.
The webspinner genus Oligotoma,
initially established by Westwood (1837) and
treated as a subgenus of Embia Latreille (1829),
currently contains 13 recognized species worldwide
(Table 2), but it is diffi cult to estimate the actual
likely number of species of these embiids. Thus,
many specimens are likely to be reclassified
The Embiopteran Genus Oligotoma Westwood, 1837 (Embioptera:
Oligotomidae), with Three New Recorded Species from Thailand
Pisit Poolprasert
ABSTRACT
Field sampling was performed at 17 locations within 14 provinces in Thailand by hand collection
from January 2008 to July 2011 and resulted in the collection of three distinct species of Oligotoma—
namely, O. humbertiana (Saussure, 1896), O. nigra (Hagen, 1885) and O. saundersii (Westwood,
1837)—that are new records for Thailand. Details of the important morphological characteristics of the
female were added and illustrated. Identifi cation keys to the three species, for both male and female
adults, were compiled and the geographic distributions of the three species in this genus in Thailand
were also mapped.
Keywords: new record, Embioptera, distribution, Thailand, Oligotoma
(Ross, 2007) for instance, analysis of embiopteran
phylogeny to test the current classification
(Szumik et al., 2008). However, the adult (imago)
male species in the genus Oligotoma, which is
closely related to the genera Aposthonia Krauss,
1911 and Eosembia Ross, 2007 (Poolprasert et al.,
2011a, b), can be distinguished from members of
the other genera by the presence of mesal lobing
of the left cercus basipodite (LCB), which is free,
prominent and ring-like, with an often pronounced
and specialized mesad. The left cercus is two-
segmented with the basal segment subcylindrical
to strongly clavated, occasionally lobed on the
inner side, but never echinulated.
In this study, involving fi eld sampling
from 17 locations within 14 provinces in Thailand,
three species of Oligotoma—O. humbertiana
(Saussure, 1896), O. nigra (Hagen, 1885) and
O. saundersii (Westwood, 1837)—were found,
which had not been previously reported in
Thailand and are therefore considered as new
records for the country. Furthermore, potential
diagnostic characteristics of the adult females are
noted between these three species based on the
differences in the patterns of their sternites. The
distribution localities in Thailand and keys to the
species of both sexes of these three species are
presented.
MATERIALS AND METHODS
Webspinner specimens were collected
as found after searching the bark of trees,
hollow twigs, lichen, moss patches and other
suitable habitats within 17 locations in 14 of
the 77 provinces in Thailand (Figure 1). At each
location, trees with fi ssured bark, intermittent
lichen or moss patches and hollow twigs among
others locations, as appropriate, were examined
and recorded for webspinners and habitat type.
Webspinners were collected and kept in plastic
boxes. The nymphal stages were brought back
alive and reared in the laboratory, using the
bark of trees, lichen and mosses from the area
they were collected in as their food, until they
developed into adults when they, along with adult
collected specimens were preserved in 95% ethyl
alcohol. Species identifi cation and measurements
were investigated using a stereomicroscope with
an ocular micrometer. For those identified as
belonging to the genus Oligotoma, the heads of the
adult male and female, male genitalia and female
sternite were illustrated using the stereomicroscope
with the aid of a drawing attachment tube.
The terminology and symbols used
in the study were the same as those employed
by Poolprasert et al. (2011a, b). Samples (both
those identifi ed to the species level and those still
Figure 1 Distribution of the three collected
species from the Oligotoma group in
Thailand.
Kasetsart J. (Nat. Sci.) 46(3)
409
Kasetsart J. (Nat. Sci.) 46(3)
410
undergoing taxonomic investigation) were then
deposited in the collection of the Chulalongkorn
University Museum of Natural History, (CUMNH)
Bangkok, Thailand.
RESULTS
Three species in the genus Oligotoma
were found for the fi rst time in Thailand—namely,
O. humbertiana, O. nigra and O. saundersii.
Comparative measurements of the character (head
width, head length, body width, body length,
forewing width, forewing length, hindwing
width and hindwing length) of the three species
are given in Table 1. The details of the important
morphological characteristics of the adult female
(apterous) are described in Figure 2.
Oligotoma humbertiana (Saussure, 1896)
(Figures 2A, 3A&B, 4A&B)
Material examined Thailand, Prachuap
Khiri Khan province, Mueang district, public park,
11°48.613’N, 098°47.329’E, 7 m, 10-24. VIII.
2009 (5 males, 5 females).
Adult male (alate) Oligotoma humbertiana
is readily recognized by the minute, outer-apical
process on the right tergal process of the tenth
abdominal segment.
Adult female (apterous) differs from
congeners by head capsule brown, longer
than broad. Eyes small and less reniform.
Mandibles massive. Antennae 19–20 segmented.
Thorax brown throughout, meso- and metaterga
smooth undivided. All legs darkish brown
throughout. Hind leg with only one basitarsal
papilla. Abdomen broad and cylindrical. Tenth
sternum symmetrically divided longitudinally
into two lateral plates. Sternite 8 divided with an
unpigmented spot area at the center and on both
lateral sides with a pattern of two unpigmented
narrow convergent lines. Sternite 9 is without a
distinct pattern.
Oligotoma nigra (Hagen, 1885)
(Figures 2B, 3C&D, 4C&D)
Material examined Thailand, Tak
province, Mae Sod district, plantation, 16°4.475’N,
098°34.291’E, 196 m, 04. IV. 2008 (1 male, 2
Table 1 Comparative measurements of three species of Oligotoma collected from Thailand.
Character O. humbertiana O. nigra O. saundersii
Male n=5, mean ± SD n=4, mean ± SD n=24, mean ± SD
Head width, mm 1.1 ± 0.02 1.1 ± 0.05 1.1 ± 0.13
Head length, mm 1.2 ± 0.05 1.2 ± 0.02 1.2 ± 0.11
Body width, mm 1.2 ± 0.03 1.2 ± 0.01 1.2 ± 0.06
Body length, mm 6.3 ± 0.29 6.5 ± 0.21 6.7 ± 0.35
Forewing width, mm 2.3 ± 0.02 2.1 ± 0.03 2.1 ± 0.22
Forewing length, mm 5.5 ± 0.14 6.3 ± 0.25 5.4 ± 0.43
Hindwing width, mm 2.1 ± 0.19 1.9 ± 0.12 2.1 ± 0.34
Hindwing length, mm 4.5 ± 0.13 5.4 ± 0.23 4.3 ± 0.44
Female n=5, mean ± SD n=6, mean ± SD n=48, mean ± SD
Head width, mm 1.1 ± 0.06 1.2 ± 0.04 1.1 ± 0.11
Head length, mm 1.2 ± 0.04 1.2 ± 0.03 1.3 ± 0.09
Body width, mm 1.2 ± 0.03 1.3 ± 0.04 1.3 ± 0.09
Body length, mm 6.5 ± 0.05 6.7 ± 0.17 6.8 ± 0.57
Kasetsart J. (Nat. Sci.) 46(3)
411
females) and Chiang Mai province, Mueang
district, Huay Kaeo Arboretum, 18°48.348’N,
098°57.585’E, 336 m, 01. III. 2008 (3 males, 4
females).
Adult male (alate) of Oligotoma nigra
can be recognized by the hook-like process of
LCB, directed ventrally, rather than horizontal as
in O. saundersii.
Adult female (apterous) can be
distinguished from congeners by head capsule
somewhat lighter particularly in clypeus;
rectangular-like small eyes. Thorax dark brown
throughout. All legs dark throughout. Hind leg
with only one basitarsal papilla. Abdomen very
dark throughout, cylindrical. Sternite 8 with
two indefi nably outlined, broad, round, lateral
pigmented areas separated medially by almost
unpigmented areas. Sternite 9 deeply inset into
the segment.
Oligotoma saundersii (Westwood, 1837)
(Figures 2C, 3E&F, 4E&F)
Material examined.- Thailand, Bangkok
province, Pathumwan district, Lumpini park,
13°45.575’N, 100°32.304’E, 7 m, 06. V. - 05.
X. 2008 (2 males, 1 female); Chulalongkorn
University 13°44.288’N, 100°31.824’E, 8 m, 10.
VII. -08. IX 2009 (2 males, 4 females); Bangkhen
district, Kasetsart University, 13°50.929’N,
100°34.239’E, 6 m, 31. VI. -14.XII.2008 (4
males, 6 females); Chiang Mai province, Mueang
district, Huay Kaeo Arboretum, 18°48.348’N,
098°57.585’E, 336 m, 21. V. 2008 (1 male);
Chiang Rai province, Mueang district, public
park, 19°58.363’N, 099° 53.212’E, 383 m, 24.
IX. 2009 (1 male, 2 females); Kalasin province,
Khao Wong district, dry dipterocarp forest,
16°45.415’N, 104°07.526’E, 280 m, 21. V. 2008
Figure 2 Light micrograph of females: A) Oligotoma humbertiana; B) O. nigra; C) O. saundersii.
(8 = eighth abdominal sternite; 9 = ninth abdominal sternite.)
Kasetsart J. (Nat. Sci.) 46(3)
412
(1 female); Nong Kai province, Mueang district,
public park, 14°58.160’N, 102°5.591’E, 182 m,
28. XI. 2009 (1 male, 1 female); Nong Bua Lam
Phu province, Naklang district, dry dipterocarp
forest, 17°12.839’N, 102°08.176’E, 293 m, 16.
VII. 2010 (4 males, 7 females); botanical garden,
17°18.557’N, 102°11.198’E, 256 m, 17. VII.
2010 (2 males, 5 females); Prachuap Khiri Khan
province, Bang Saphan district, botanical garden,
11°19.124’N 099°24.422’E, 80 m, 03. VIII. 2009
(3 females); Prachuap Khiri Khan province,
Mueang district, plantation, 11°148.613’N
099°47.329’E, 7 m, 01. VIII. 2009 (1 male, 2
females); Petchabun province, Lom Sak district,
plantation, 16°46.462’N, 101°14.323’E, 129 m,
27. X. 2010 (1 female); Petchaburi province, Ban
Lad district, orchard, 13°02.428’N 099°53.043’E,
8 m, 12. VII. 2009 (2 females); Ratchaburi
province, Suan Phueng district, botanical garden,
13°32.805’N, 099°20.126’E, 134 m, 22. VIII -18.
IX. 2009 (5 males, 7 females); Sa Kaeo province,
Aranyaprathet district, public park, 13°48.531’N,
102°04.193’E, 102 m, 15. VII. 2011 (2 females);
Satun province, Mueang district, public park,
06°37.242’N, 100°4.021’E, 25 m, 22. X. 2008 (1
male, 3 females); Trang province, Mueang district,
public park, 07°33.255’N, 099°36.831’E, 22 m,
02. XII. 2010 (1 female).
Adult male (alate) of Oligotoma
saundersii is easily recognized by the horizontal
sickle-shaped process beneath the hypandrium
lobe.
Adult female (apterous) differs from
congeners as head capsule darkish brown, longer
than width. Eyes small. Antennae, 20 short
segments. Thorax darkish brown throughout.
All legs dark throughout. Hind leg with only one
basitarsal papilla. Abdomen chocolate-brown
throughout, broad and cylindrical. Sternite 8 is
divided into a medial with two narrow, caudally
convergent membranous lines. Sternite 9 is arrow
headed in shape within the body.
Key to three Thai species of the genus Oligotoma
(Adult males)
The identifi cation key was modifi ed from Ross
(1940 and 1944).
Abbreviations used in the key are: 10LP = left
tergal process; 10RP = right tergal process; H
= hypandrium (sternite 9); LCB = left cercus-
basipodite; LPPT = left paraproct.
1. 10LP broad, constricted basally thence broad
subapically. 10RP long, gradually distended
with smaller sharp projection at extremity.
H broad, transverse basally with left apical
angle-like narrow sickle spine. LCB broadest
ventrally, produced mesad as narrow, simple,
rounded lobe (Figures 3E&F). ...O. saundersii
(Westwood)
- 10LP narrow (Figures 3A-D).......................2
2. 10LP small, curved, slightly leftward with
small outer hook. 10RP long subparallel sided
with distinct subapical tooth on outer side. H
broad basally gradually narrowed distally. LCB
adjoins dorso-posterio-mesad with double
lobe; basal portion blunt rounded (Figures
3A&B).................O. humbertiana (Saussure)
- 10LP gradually arced leftward, tapered to apex.
10RP long, gradually narrowed distally; LPPT
with ventrally hook, slightly curved rightward.
H broad, transverse basally, abruptly narrowed.
LCB produced mesad, bilobed (Figures 3
C&D)............................................O. nigra
(Hagen)
Key to the three Thai species of the genus
Oligotoma (Adult females)
1. Head quadrated-oval. Sternite 8 with two
indefinably outlined, broad, round, lateral
pigmented areas separated medially by almost
unpigmented areas. Sternite 9 deeply inset into
segment (Figures 4C&D)...............................
O. nigra (Hagen)
- Head, longer than broad (Figures 4A&B, 4E
&F)...............................................................2
Kasetsart J. (Nat. Sci.) 46(3)
413
2. Sternite 8 divided into a medial with two
narrow, caudally convergent membranous
lines. Sternite 9 is arrow headed in the shape
within body (Figures 4E&F)..........................
O. saundersii (Westwood)
- Sternite 8 divided with unpigmented spot
area at center and on both lateral sides with
pattern of two unpigmented narrow convergent
lines. Sternite 9 without distinct pattern (Figs.
4A&B). ...............O. humbertiana (Saussure)
DISCUSSION AND CONCLUSION
The three species of Oligotma
(Oligotomidae)—O. humbertiana, O. nigra and
O. saundersii—are the fi rst records from Thailand
(Table 2).
The oligotomids are potentially one of
the largest genera of Embiopteran and they are
relatively common and cosmopolitan because
of their rapid (anthropogenic) colonization and
proliferation rates, being spread by humans
throughout tropical Asia (Ross, 2007; Poolprasert
et al., 2011a). However, they have remained
largely unrecorded. The results from the current
study have increased the information on the
distribution of the genus Oligotoma in Thailand.
All three of the species reported here
predominately occur in northern India (Ross,
2000b), but O. humbertiana is very common in
Figure 3 Important characters of males Oligotoma humbertiana (A&B), O. nigra (C&D) and O.
saundersii (E&F). A, C, E) Dorsal views of terminalia. B, D, F) Ventral views of terminalia.
(10LP and 10RP = left and right tergal processes; EP = epiproct (segment 11); H = hypandrium
(sternite 9); HP = hypandrium process; LCB = left cercus-basipodite; LC
1
and LC
2
= fi rst and
second segments of left cercus; RC
1
and RC
2
= fi rst and second segments of right circus.)
Kasetsart J. (Nat. Sci.) 46(3)
414
Figure 4 Important characters of females Oligotoma humbertiana (A&B), O. nigra (C&D) and O.
saundersii (E&F). A, C, E) Head. B, D, F) Ventral views of terminalia. (8 = eighth abdominal
sternite; 9 = ninth abdominal sternite.)
eastern and southern Asia, including now being
recorded in Thailand, albeit thus far only at a
single locality in Prachuap Khiri Khan province.
O. saundersii is likely to be found in either tropical
or temperate zones, and in this study in Thailand,
it was the most common of the three species,
being found in 13 provinces (Table 3). O. nigra is
widely found in the Middle East and the Red Sea
region (Ross, 2006), and now also extends into the
southern United States as an introduced species
(Ross, 1957), in addition to other localities where
it can be found. Presently, it has been identifi ed in
western and northern Thailand.
These three Thai embiids within the
genus Oligotoma can be found in various habitat
types either in forests or in human exploited
areas. The majority of habitats where the three
oligotomids in this study were found was in the
bark of shaded trees and near residential areas,
such as in public parks and gardens, although some
were also found in dry dipterocrap or dry evergreen
forests. The habits of O. humbertiana have been
rather extensively described (Ling, 1934a, 1934b;
Ananthasubramanian, 1957; Edgerly, 1997), and
the observations in the current survey have mostly
concurred with them. O. humbertiana was present
under the bark of Cassia fi stula and inside the
hollows of dry twigs (Table 3). It tends to be a
solitary embiid being found alone in galleries.
Oligotoma nigra was found in ornamental
trees (Table 3) located around villages and gardens.
This genus appears to prefer dry areas (Ross,
2006), and was apparently introduced into the
southern United States in date palm cuttings
(Ross, 1957), but in western and northern Thailand
(Tak and Chiang Mai provinces), it has not been
reported to be occupying natural habitats.
Kasetsart J. (Nat. Sci.) 46(3)
415
Table 3 Oligotoma species from Thailand associated with host plants.
Oligotoma spp. Locality Host plants Site found
O. humbertiana Prachuap Khiri Khan Cassia fi stula L. Under bark
O. nigra Chiang Mai, Tak Mascarena lagenicaulis L., Bark crevice
Roystonea regia (Kunth)
Cook
O. saundersii Bangkok, Chiang Acacia auriculaeformis A. Outer /under
Mai, Chiang Rai, Cunn. Ex Benth, bark, bark
Kalasin, Nong Bua Cassia javanica L., crevice
Lam Phu, Nong Diospyios rhodcalyx Kurz,
Khai, Prachuap Khiri Eucalyptus camaldulensis
Khan, Petchabun, Dehnh, Mangifera indica
Petchaburi, L., Pterocarpus indicus
Ratchaburi, Sa Kaeo, Willd, Pithecellobium dulce
Satun, Trang (Roxb.) Benth, Shorea
roxburghii G. Don,
Tamarindus indica L.
Table 2 List of worldwide Oligotma species currently known (recognized) and their distribution
(countries).
No. Species Distribution
1. O. asymmetrica Menon & George, 1936 India
2. O. burmana Ross, 2007 Myanmar
3. O. dharwariana Bradoo, 1971 India
4. O. dichroa Navas, 1934 Vietnam
5. O. falcis Ross, 1943 India
6. O. greeniana Enderlein, 1912 China, Hong Kong, India, Malaysia,
Philippines, Singapore, Sri Lanka, Taiwan
7. O. humbertiana (Saussure, 1896) China, Hong Kong, India, Indonesia,
Madagascar, Mariana Islands, Mexico,
Philippines, Sri Lanka, Taiwan, Thailand*
8. O. josephi (Bradoo, 1971) India
9. O. nigra (Hagen, 1866) Australia, Egypt, India, Iraq, Israel, Mexico,
Thailand*, USA
10. O. pruthii Kapur & Kripalani, 1957 India
11. O. saundersii (Westwood, 1837) Australia, Brazil, Cuba, India, Indonesia,
Korea, Madagascar, Marcus Island, Mexico,
New Caledonia, Taiwan, Thailand*, U.S.A,
Venezuela, Virgin Islands.
12. O. termitophila Wasmann, 1904 Sudan
13. O. ubicki Ross, 2007 Myanmar
* = New record.
Kasetsart J. (Nat. Sci.) 46(3)
416
In contrast, during the dry season,
Oligotoma saundersii was never found inhabiting
exposed places, but rather was hiding in crevices
and under the bark of trees and in other humid
and shady places. This probably shows its
preference for a moist atmosphere. In addition,
Oligotoma saundersii tended to inhabit the bark
crevices of trees, the most common being Acacia
auriculaeformis, Cassia javanica, Mangifera
indica, Pithecellobium dulce and Tamarindus
indica (Table 3). The social habits and maternal
care of these insects, as observed during this study
at collection sites and in laboratory rearing (data
not shown), were consistent with the well-known
habits that have been reported before for this
species in other localities (Edgerly et al., 2002; Lee
et al., 2002). Because they tend to live in groups
that adopt shared breeding sites and cooperate in
brooding care, they are considered as communal
colonies.
From this survey alone, there are still
10 specimens that are unclassifi ed to the species
level; thus, further elaboration would likely further
change the poorly known embiid fauna status in
Thailand. In addition, this study did not cover a full
geographic range of likely habitat in the country,
so further surveys are still required and are likely
to reveal more new records for Thailand.
ACKNOWLEDGEMENTS
This research was partially supported by
the Offi ce of the Higher Education Commission and
the Thai government budget in 2009. The author
thanks Associate Professor Chariya Lekprayoon,
Department of Biology, Chulalongkorn University,
Mr. Stuart Granger, London, UK and Dr. Janice
Edgerly Rooks, Department of Biology, Santa
Clara University, U.S.A. for reviewing and
comments on the manuscript. Finally, gratitude is
expressed to Dr. Edward Ross, California, U.S.A.
for support while visiting his collection.
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