Cyrtophora exanthematica
Encyclopedia
Cyrtophora exanthematica are tent spiders
common in tropical Asia
and Australia
. They are commonly known as double-tailed tent spiders because of the pair of blunt projections at the end of their abdomens. They are harmless to humans.
Double-tailed tent spiders build large nonsticky webs of two parts – a tangle web and a finely-meshed horizontal orb web. The females of the species are larger than the males and they may vary considerably in colour. They are easily distinguishable by their shape, the markings on their backs, and the way the females have the habit of guarding their eggs by splaying their bodies over them.
'double-tailed tent spider' comes from the pair of blunt projections at the posterior end of their abdomens
. They are also known under other common names in Australia
, including dome spider, bowl spider, pan-web spider, and scoop-web spider.
Like other members of the genus Cyrtophora, the upper side of the cephalothorax
of double-tailed tent spiders are flattened. The cephalothorax, the sides of the abdomen, and the legs are covered with white hairs. Its leg formula is I,II,III,IV – that is, the longest legs are the first pair at the front, the second pair the next longest, the third pair shorter than the second, and the last pair the shortest. The eight eyes are more or less of equal size and arranged in two recurved rows.
They also possess the characteristic pair of humps on the front side of their abdomen, somewhat resembling 'shoulders' and giving them the distinctive triangular shape. On the upper side are eight prominent sigilla (small pit-like depressions) arranged in two rows. The abdomen is subrectangular, with somewhat flat sides, and has small tubercules at the front. It is longer than it is wide and tapers down towards the rear. The bottom side of the abdomen is usually brown with yellow book lung
s. The spinneret
s are rimmed with white. The epigynum
in females possesses a short triangular scape (or ovipositor
). The sperm receptacles (spermatheca
e) are globular.
They can vary considerably
in colour. They can be red, pink, orange, yellow, brown, grey, pale brown, or completely black. In some individuals two somewhat wavy and sometimes 'beaded' chalk-white line patterns are clearly visible, running from the front of the abdomen, to the tip of the 'humps', and down to below its pair of 'tails'. In others, they are only present as faint lines.
Double-tailed tent spiders are sexually dimorphic
, with the males generally far smaller than the females. Female adults average around 10 mm (0.393700787401575 in) in length (excluding the legs), but can reach up to 15 mm (0.590551181102362 in). Male adults average only 3.5 to 6 mm (0.137795275590551 to 0.236220472440945 in), with the abdomen about the same size as the cephalothorax and with prominent pedipalp
s.
Double-tailed tent spiders closely resemble Cyrtophora parangexanthematica
in the Philippines
. A fact reflected by its scientific name which literally means "like exanthematica" in Filipino
.
military surgeon Carl Ludwig Doleschall
while stationed in Java
in 1859 with the Dutch
army. He originally classified it under the genus Epeira (which is now the genus Araneus
). They are currently classified under the genus Cyrtophora
(tent-web spiders) under subfamily Cyrtophorinae
. They belong to the very large orb-weaver spider
family
(Araneidae).
The generic name
Cyrtophora means "curve bearer", from Greek
(, meaning 'bent' or 'curved') and (, meaning 'bearer' or 'carrying'), referring to the shape of the abdomen of the members of the genus. The specific name "exanthematica" comes from the Greek (, meaning 'pimple') and the suffix
(, meaning 'pertaining to'), a reference to its appearance.
.
The spider stays in the middle of the lower orb web hanging upside down. When it feels threatened, however, it will run to the edge of the web and hide among the vegetation and debris. The spider has a sanctuary at the edge of the web surrounded by dead leaves which it can use to camouflage itself. The male of the species can also inhabit the same web as the female.
The webs are permanent. Over time, they will begin gathering leaves and other debris. Double-tailed tent spiders will regularly clean their webs, usually at night, though they will retain some bits and pieces of debris for camouflage. The webs sometimes have to be rebuilt when severely damaged.
Double-tailed web spiders mate during summer. After mating, the female will lay her eggs in an egg sac (an ovoid ball of spider silk) in her sanctuary. She then stretches her body over the surface of the egg sac and guards it. This behavior is distinctive and makes the species easy to recognise. The mother does not feed nor leave the sanctuary until the eggs have hatched, which is usually after two or three weeks. Only then will she return to the center of the web and resume her normal activities. The spiderling
s will remain in her sanctuary for a few more weeks before setting out on their own.
Because of the relatively large size of web, they are often infested with kleptoparasitic split-faced silver spiders (Argyrodes fissifrons). While able to build webs of their own, dewdrop spiders (genus Argyrodes
) prefer to live and even reproduce in the webs of other spiders, stealing prey in the process. They can be permanently associated with one web or move around between several other tent webs in the immediate vicinity. The size of the web is directly proportional to the number of A. fissifrons inhabiting them. The relationships can sometimes be commensal
or even mutual, as A. fissifrons eat prey entangled in the webs that are too small for the larger double-tailed tent spiders. However, they often help themselves to food stores or even food in the process of being consumed by the hosts as well. Larger individuals are more audacious, but they usually stay on the tangle webs and out of the way of their hosts. Double-tailed tent spiders seem to tolerate their presence though they sometimes have to shove them away when they catch larger prey.
and Australia
. Their native range
extends from Australia
to southern Japan
and from the Philippines
and Papua New Guinea
to as far west as India
. They usually build their permanent webs on the branches of trees or shrubs.
The silk of double-tailed tent spiders are also among those being studied for possible applications in creating nanocapsules and microcapsules.
Cyrtophora
The Tent-web spiders , although technically orb-web spiders , do not build orb webs. Their tent-like, highly complex non-sticky web is sometimes considered a precursor of the simplified orb-web. These webs are aligned horizontally, with a network of supporting threads above them. These spiders...
common in tropical Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. They are commonly known as double-tailed tent spiders because of the pair of blunt projections at the end of their abdomens. They are harmless to humans.
Double-tailed tent spiders build large nonsticky webs of two parts – a tangle web and a finely-meshed horizontal orb web. The females of the species are larger than the males and they may vary considerably in colour. They are easily distinguishable by their shape, the markings on their backs, and the way the females have the habit of guarding their eggs by splaying their bodies over them.
Description
Their common nameCommon name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
'double-tailed tent spider' comes from the pair of blunt projections at the posterior end of their abdomens
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
. They are also known under other common names in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, including dome spider, bowl spider, pan-web spider, and scoop-web spider.
Like other members of the genus Cyrtophora, the upper side of the cephalothorax
Cephalothorax
The cephalothorax is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. The word cephalothorax is derived from the Greek words for head and thorax...
of double-tailed tent spiders are flattened. The cephalothorax, the sides of the abdomen, and the legs are covered with white hairs. Its leg formula is I,II,III,IV – that is, the longest legs are the first pair at the front, the second pair the next longest, the third pair shorter than the second, and the last pair the shortest. The eight eyes are more or less of equal size and arranged in two recurved rows.
They also possess the characteristic pair of humps on the front side of their abdomen, somewhat resembling 'shoulders' and giving them the distinctive triangular shape. On the upper side are eight prominent sigilla (small pit-like depressions) arranged in two rows. The abdomen is subrectangular, with somewhat flat sides, and has small tubercules at the front. It is longer than it is wide and tapers down towards the rear. The bottom side of the abdomen is usually brown with yellow book lung
Book lung
A book lung is a type of respiration organ used for atmospheric gas exchange and is found in arachnids, such as scorpions and spiders. Each of these organs is found inside a ventral abdominal cavity and connects with the surroundings through a small opening. Book lungs are not related to the lungs...
s. The spinneret
Spinneret
A spinneret is a spider's or insect larva's silk-spinning organ. It is usually on the underside of a spider's abdomen, to the rear. While most spiders have six spinnerets, some have two, four, or eight. They move independently and in concert...
s are rimmed with white. The epigynum
Epigyne
The epigyne or epigynum is the external genital structure of female spiders. As the epigyne varies greatly in form in different species, even in closely related ones, it often provides the most distinctive characteristic for recognizing species...
in females possesses a short triangular scape (or ovipositor
Ovipositor
The ovipositor is an organ used by some animals for oviposition, i.e., the laying of eggs. It consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and to place it properly...
). The sperm receptacles (spermatheca
Spermatheca
The spermatheca , also called receptaculum seminis , is an organ of the female reproductive tract in insects, some molluscs, oligochaeta worms and certain other invertebrates and vertebrates...
e) are globular.
They can vary considerably
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
in colour. They can be red, pink, orange, yellow, brown, grey, pale brown, or completely black. In some individuals two somewhat wavy and sometimes 'beaded' chalk-white line patterns are clearly visible, running from the front of the abdomen, to the tip of the 'humps', and down to below its pair of 'tails'. In others, they are only present as faint lines.
Double-tailed tent spiders are sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
, with the males generally far smaller than the females. Female adults average around 10 mm (0.393700787401575 in) in length (excluding the legs), but can reach up to 15 mm (0.590551181102362 in). Male adults average only 3.5 to 6 mm (0.137795275590551 to 0.236220472440945 in), with the abdomen about the same size as the cephalothorax and with prominent pedipalp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...
s.
Double-tailed tent spiders closely resemble Cyrtophora parangexanthematica
Cyrtophora parangexanthematica
Cyrtophora parangexanthematica is a species of tent spider found in the Philippines. Its scientific name comes from its close resemblance to double-tailed tent spiders. It was described from a single female specimen collected in 1995.-Taxonomy:...
in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. A fact reflected by its scientific name which literally means "like exanthematica" in Filipino
Filipino language
This move has drawn much criticism from other regional groups.In 1987, a new constitution introduced many provisions for the language.Article XIV, Section 6, omits any mention of Tagalog as the basis for Filipino, and states that:...
.
Taxonomy
Double-tailed tent spiders were first described by the SlovakianSlovaks
The Slovaks, Slovak people, or Slovakians are a West Slavic people that primarily inhabit Slovakia and speak the Slovak language, which is closely related to the Czech language.Most Slovaks today live within the borders of the independent Slovakia...
military surgeon Carl Ludwig Doleschall
Carl Ludwig Doleschall
Carl Ludwig Doleschall was born in Nové Mesto nad Váhom , Slovakia , as the son of the theologian Michael Doleschall, and died in Ambon Island, Moluccas, only 31 years old...
while stationed in Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...
in 1859 with the Dutch
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
army. He originally classified it under the genus Epeira (which is now the genus Araneus
Araneus
Araneus is a genus of common orb-weaving spiders. It includes about 650 species, among which are the European garden spider and the barn spider.-Description:...
). They are currently classified under the genus Cyrtophora
Cyrtophora
The Tent-web spiders , although technically orb-web spiders , do not build orb webs. Their tent-like, highly complex non-sticky web is sometimes considered a precursor of the simplified orb-web. These webs are aligned horizontally, with a network of supporting threads above them. These spiders...
(tent-web spiders) under subfamily Cyrtophorinae
Cyrtophorinae
Cyrtophorinae is a subfamily of spiders in the orb-weaver spider family. Unlike other orb-weavers, spiders belonging to Cyrtophorinae build horizontal, finely meshed platforms within a tangle of irregular webs...
. They belong to the very large orb-weaver spider
Orb-weaver spider
The "typical" orb-weaver spiders are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields and forests...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
(Araneidae).
The generic name
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Cyrtophora means "curve bearer", from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
(, meaning 'bent' or 'curved') and (, meaning 'bearer' or 'carrying'), referring to the shape of the abdomen of the members of the genus. The specific name "exanthematica" comes from the Greek (, meaning 'pimple') and the suffix
Suffix
In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs...
(, meaning 'pertaining to'), a reference to its appearance.
Ecology
Double-tailed tent spiders usually build their webs in branches of trees or shrubs, using surrounding leaves and twigs as a framework. The webs are composed of two distinct parts. The upper section is an irregular dense mass of random supporting webs (known as a 'tangle web'). It serves to discourage prey from entering from the top of the web complex. At the bottom is a horizontally-oriented, exceptionally finely-meshed web (the 'orb web') about 0.5 m (1.6 ft) in diameter. Like those of other tent-web spiders, this web is somewhat tent-like. Unlike the others, however, the orb webs of double-tailed tent spiders are often shaped more like a pan or a bowl. No part of the web is sticky, unlike the webs of other orb-weaversOrb-weaver spider
The "typical" orb-weaver spiders are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields and forests...
.
The spider stays in the middle of the lower orb web hanging upside down. When it feels threatened, however, it will run to the edge of the web and hide among the vegetation and debris. The spider has a sanctuary at the edge of the web surrounded by dead leaves which it can use to camouflage itself. The male of the species can also inhabit the same web as the female.
The webs are permanent. Over time, they will begin gathering leaves and other debris. Double-tailed tent spiders will regularly clean their webs, usually at night, though they will retain some bits and pieces of debris for camouflage. The webs sometimes have to be rebuilt when severely damaged.
Double-tailed web spiders mate during summer. After mating, the female will lay her eggs in an egg sac (an ovoid ball of spider silk) in her sanctuary. She then stretches her body over the surface of the egg sac and guards it. This behavior is distinctive and makes the species easy to recognise. The mother does not feed nor leave the sanctuary until the eggs have hatched, which is usually after two or three weeks. Only then will she return to the center of the web and resume her normal activities. The spiderling
Spiderling
Spiderling may refer to:* an immature spider* the herbaceous plant genus Boerhavia...
s will remain in her sanctuary for a few more weeks before setting out on their own.
Because of the relatively large size of web, they are often infested with kleptoparasitic split-faced silver spiders (Argyrodes fissifrons). While able to build webs of their own, dewdrop spiders (genus Argyrodes
Argyrodes
Spiders of the genus Argyrodes , also called dewdrop spiders, occur worldwide. They are best known as kleptoparasites: they steal other spiders' prey. They invade and reside in their host's web even though they can spin their own webs...
) prefer to live and even reproduce in the webs of other spiders, stealing prey in the process. They can be permanently associated with one web or move around between several other tent webs in the immediate vicinity. The size of the web is directly proportional to the number of A. fissifrons inhabiting them. The relationships can sometimes be commensal
Commensalism
In ecology, commensalism is a class of relationship between two organisms where one organism benefits but the other is neutral...
or even mutual, as A. fissifrons eat prey entangled in the webs that are too small for the larger double-tailed tent spiders. However, they often help themselves to food stores or even food in the process of being consumed by the hosts as well. Larger individuals are more audacious, but they usually stay on the tangle webs and out of the way of their hosts. Double-tailed tent spiders seem to tolerate their presence though they sometimes have to shove them away when they catch larger prey.
Distribution and habitat
Double-tailed tent spiders are widespread in tropical AsiaAsia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Their native range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
extends from Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
to southern Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and from the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
and Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
to as far west as India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
. They usually build their permanent webs on the branches of trees or shrubs.
Relations with humans
Like other tent-web spiders, double-tailed tent spiders are very shy. When threatened they will usually run away or play dead (also known as thanatosis). They are not aggressive to humans and they are unlikely to bite humans unless severely provoked. No bites have been recorded.The silk of double-tailed tent spiders are also among those being studied for possible applications in creating nanocapsules and microcapsules.
External links
- Cyrtophora exanthematica Doleschall, 1859 Double Tailed Tent Spider at Arachne.org.au
- Pan-web Spider – Cyrtophora exanthematica at Brisbane Insects and Spiders
- Tent spiders at the Queensland Museum Official Website
- Cyrtophora exanthematica at the Find-a-spider Guide
- Riceland spiders of South and Southeast Asia by A. T. Barrion, J. A. Litsinger, and the International Rice Research InstituteInternational Rice Research InstituteThe International Rice Research Institute is an international NGO. Its headquarters are in Los Baños, Laguna, Philippines, and it has offices in sixteen countries...
. A book freely available for non-commercial use under CC-BY-NC-SA.