Argiope aemula

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Oval St Andrew's Cross Spider
Female Argiope Aemula Spider Mysore Jan24 D72 25682.jpg
Female (dorsal), Mysore, India
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Infraorder: Araneomorphae
Family: Araneidae
Genus: Argiope
Species:
A. aemula
Binomial name
Argiope aemula
(Walckenaer, 1841) [1]

Argiope aemula, commonly known as the oval St Andrew's cross spider, is a species of spider in the family Araneidae which is native to southeast Asia, found from India and Sri Lanka to the Philippines, Indonesia, and Vanuatu. [1] It is one of the giant, conspicuous "signature spider" species of the genus Argiope , observed in tropical and subtropical grasslands.

Contents

Taxonomy and naming

Etymology

The term Argiope comes from the Greek Αργιόπη, "silver face" (sharing a common root with the Latin word for silver, argentum), referring to the fact that the spiders in this group have silky silver hairs covering their carapaces. [2]

Common and alternate scientific names

They are commonly known as the oval St. Andrew's cross spider, which can be confusing because several other Argiope species are also commonly called "St. Andrew's cross spiders". An alternate scientific name for the species is Argiopenigripes.

Phylogeny

Argiope aemula is part of the Araneidae family. They are in the same genus as common spiders such as Argiope aurantia, or the yellow garden spider, and the Argiope argentata, or the silver Argiope. [3]

Description

The female is larger than male - often reaching 25–30 mm while the male tends to stop growing at 5–8 mm. Its Cephalothorax is brownish with a white pubescence. Its posterior median eyes are encircled in black and its sternum is heart shaped. Further, there is a narrow elongation found at the distal end of sternum. Its oval shaped and anteriorly truncated abdomen is yellowish with black stripes. Its ventrum is brownish with yellow parallel lines. [4]

Argiope aemula has silver hairs on its carapace - hence its namesake. The female spider has a carapace that is flat with yellow and black horizontal lines that are present from the end of the carapace to the entirety of the backside. [3] The spider has eight legs that are doubled up and spread like an X in the web. The legs are long with claw like structures at the end. Their legs have grey color and black rings around them. The cephalothorax is a dirty white color and the sternum is shaped like a heart. [5] There are four yellow dots that are placed in its abdomen and are organized vertically. The females’ exotic color has been speculated to be associated with prey attraction. Males are much less brilliant in their color. Their sternum and backside are brownish while their carapace is black. Both sexes have abdomens that are oval shaped. They are easy to identify thanks to their stabilimentum in their web. Males are 5–8 mm while females are 23–30 mm creating a large size dichotomy. [2]

Distribution and habitat

Distribution

These spiders are found largely in South East Asian countries such as the Philippines, Malaysia, Singapore, and Thailand. They can also be seen in India, Sri Lanka, China, northern Australia, and southern Japan. [2]

Habitat

They are found near human settlements and they prefer woodland in sunny locations where there are flowers, shrubby, and plants to give them protection. Vegetation species such as big bidens and giant false sensitive plants are common in their habitat. They tend to have their webs around 1–2 m above the ground. [2]

Mating

When the male arrives at the female's web, he begins courtship. After courtship, the male inserts his palpal bulb into the female. This is known as the first insertion. After the first insertion, the male then jumps away from the female. Some males are eaten before they can escape. If they can successfully escape, the male begins the second insertion. Around half the time, the second insertion is successful while the other half, the male is eaten after the first insertion. [6]

Sexual cannibalism

In most cases, males are cannibalized when or after they insert their palpal bulb. If males are not cannibalized during the first insertion, they are almost guaranteed to get eaten after the second insertion. In fact, in most cases, males lie motionless after completing the second insertion, possibly dying or having died. This contrast with how after the first insertion, males aggressively resist cannibalism. These observations have led to the theory that males welcome sexual cannibalism after the second insertion. Sexual cannibalism may be favored by natural selection as it provides resources to the female. This can improve the reproductive success of the female and therefore help the males' genes be passed on. Sexual cannibalism is most likely to occur if the male only mates once in his lifetime. Even when males survive the second insertion, they often die the following day, indicating that being cannibalized may be part of their natural behavior. [5] [7]

Behavior

Size-affected behavior

When the spiders are less than 23 mm, they build discoid decorations. When they get larger than 23 mm, they tend to build cruciate decorations. Furthermore, mature Argiope aemula that are less than 10 mm long build webs deep inside the vegetation rather than out in the open. This is likely due to the fact that they require extra protection due to their size. [2]

Hunting and predation

Prey capture

The most likely hypothesis for the web decorations are for prey capture. Studies have suggested that the greater the capture area and the less visible the webs, the greater the capture success rate. Generally, the smallest sized web is around 2 m2. In general, the decorated webs are 60% more likely to capture prey than undecorated webs. Some of the prey for the spider includes Hymenoptera (e.g. wasps and ants), Diptera (flies), and Orthoptera (e.g. grasshoppers and crickets). Furthermore, decorated webs with spiders on the webs catch much more prey than decorated webs without spiders. Decorated webs without spiders, however, still catch more prey than webs without decorations. Web decorations have been suggested to mimic the pattern of pollen resources that prey insects are attracted to. In some cases, prey have been known to associate decorations with the spiders and avoid them. This is especially true if they have been caught in the web before (and were able to escape), as the prey will know that the decorations are a trap. However, because there are much more pollen resources than spider decorations, most prey will associate the decorations with food rather than a predator. When comparing the ultraviolet radiating pattern of the decorated webs and the pollen resources, they exhibited similar patterns indicating why prey can be confused. Furthermore, the design on the bodies of the spiders also serve as a lure. The prey of these spiders prefer patterns that are both symmetric and disrupted. These spiders have patterns that match this criterion. They have symmetric horizontal black and yellow lines with disrupted patterns on their legs. This attractive pattern and the lure of the decorated webs are most likely why decorated webs with spiders on them caught the most prey. [2] [3] [8]

Predation risk

Medium spiders are at most risk for predation. In an experiment with mud dauber wasps, the predator of Argiope aemula, they chose only a specific range of female spiders, 24–27 mm, to eat. In an experiment that measured predator attacks, almost all of the attacks were on medium-sized spiders whilst only one out of 18 was on a large spider. It has been suggested that wasps use the cruciate decorations as an indicator for the location of the spiders. [2]

Trade off between prey capture and predation risk

There exists a tradeoff between prey capture and predation risk. Decorated webs capture much more prey but also increase the risk of predation. Interestingly, despite being targeted the most, medium-sized spiders had the greatest frequency for building decorations. This could be attributed to a strategy for medium-sized spiders. The strategy is that they are willing to take the risk of being predated in return for the increased capture success that they get using decorated webs. This is so that they can quickly become a large spider and grow out of being the vulnerable medium size. Therefore, there are two selection pressures going against each other. One selection pressure causes them to create brilliantly decorated webs as they attract more prey and allow them to grow out of the venerable size. However, another selection pressure suggests them to stop building decorated webs as they attract predators. Therefore, the genetic and physiological status of the spiders often sway this decision into one way or another. The genetic component of this is particularly evident in the fact that the amount of silk reserve in the spiders’ silk glands vary from spider to spider. This quantity of available silk may influence the amount of silk they can produce and therefore the size of their webs. [2] [3]

Web design

Web decoration

A majority of orb web spiders, including Argiope aemula, have decorated webs otherwise known as stabilimentum. The spiders generally tend to use eggs, waste, or prey to create their decorations. In some cases, the decorations are entirely made of the spider's silk. The purpose of the decorations are not exactly clear, although they have been speculated to serve purposes such as prey capture or camouflage against predators. However, recent studies have indicated that when viewed against the background vegetation, the decorations are highly visible showing that it may not serve as camouflage. Furthermore, these studies have suggested that the silk decorations can actually attract predators. The study conducted showed that when the spiders’ predator, praying mantids, were placed in a cage, they chose decorated webs more often than undecorated webs. An interesting observation was that in the presence of predators, these spiders reduced the size and building frequency of the webs. On the other hand, a study showed that blue jays attacked spiders with decorated webs less often. This could be due to the fact that the blue jays have learnt not attack webs as they are sticky and have associated the stickiness with the decorations. [2] [8] [9]

Adjustment of web decoration

Argiope aemula are able to understand its environment, forecast its potential prey accordingly, and adjust web decorations to fit the prey that they are anticipating. For example, when there are only small prey in the area, the spiders will build narrow mesh like webs to capture these small prey. They also made the height of their webs lower. Furthermore, starved spiders were much more likely to build larger webs than well-fed spiders. Not only did starved spiders build larger webs, they also increased their capture area. This adjustment capability illustrates the fact that these spiders are able to observe its surroundings and make rationalized decisions based on the given input. The starved spiders also made the mesh in the webs narrower. This is likely due to the fact that they were unable to tell the size of the prey and therefore made it the smallest it could to be able to capture any prey. Spiders also adjusted the distance between sticky spirals. Starved spiders created spirals with smaller distances between each other likely to be able to capture more prey. Finally, spiders also created more spiral turns whilst reducing the distance between each turn. This was done so likely because increased spiral turns meant greater capture area, but it also meant more resources expended. Therefore, by reducing the distance between each spiral turn, the spiders were able to create greater capture area whilst expending as little energy as possible. [3] [9]

Ecology

Signature spiders get their name from the zigzag design embossed on the web, the stabilimentum, that is believed to serve a camouflage function. They show extreme sexual dimorphism and males are only 10% of the female in size and as a result become victims of sexual cannibalism. If the males survive the first copulation, then they almost always die during the second attempt. [5] However, further studies have shown that male invariably dies after second copulation as a form of programmed suicide. [10]

Venom

Argiope aemula have venom. However, the venom of these spiders are not a serious threat to humans. Their venom contains polyamine toxins that are sometimes used against prey if they are still alive. When humans get bit, there is some swelling although no medical attention is needed. [11]

Related Research Articles

<i>Argiope</i> (spider) Genus of spiders

The genus Argiope includes rather large spiders that often have a strikingly coloured abdomen. These spiders are distributed throughout the world. Most countries in tropical or temperate climates host one or more species that are similar in appearance. The etymology of Argiope is from a Latin word argentum meaning silver. The carapace of Argiope species is typically covered in silvery hairs, and when crawling in the sun, they reflect it in a way that gives them a metallic, white appearance.

<span class="mw-page-title-main">Orb-weaver spider</span> Family of spiders

Orb-weaver spiders are members of the spider family Araneidae. They are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields, and forests. The English word "orb" can mean "circular", hence the English name of the group. Araneids have eight similar eyes, hairy or spiny legs, and no stridulating organs.

<span class="mw-page-title-main">Stabilimentum</span> Conspicuous, usually zig-zagged, silk structure in some orb-weaver spider webs

A stabilimentum, also known as a web decoration, is a conspicuous silk structure included in the webs of some species of orb-web spider. Its function is a subject of debate.

<i>Argiope keyserlingi</i> St Andrews cross spider

Argiope keyserlingi is a species of orb-web spider found on the east coast of Australia, from Victoria to northern Queensland. It is very similar in appearance to a closely related north Queensland species, Argiope aetherea. A. keyserlingi is commonly found in large populations in suburban parks and gardens, particularly among the leaves of Lomandra longifolia. Like many species of orb-web spider, A. keyserlingi shows considerable sexual dimorphism, as the females are many times larger than the males. Mature females can be seen during the summer, and seeing multiple males on the web of one female is not uncommon.

<span class="mw-page-title-main">Argiope bruennichi</span> Species of orb-weaver spider.

Argiope bruennichi is a species of orb-web spiders distributed throughout Central and Northern Europe, North Africa, parts of Asia, and the Azores archipelago. Like many other members of the genus Argiope, it has strikingly yellow and black markings on its abdomen.

<i>Argiope aurantia</i> Species of spider

Argiope aurantia is a species of spider, commonly known as the yellow garden spider, black and yellow garden spider, golden garden spider, writing spider, zigzag spider, zipper spider, black and yellow argiope, corn spider, Steeler spider, or McKinley spider. The species was first described by Hippolyte Lucas in 1833. It is common to the contiguous United States, Hawaii, southern Canada, Mexico, and Central America. It has distinctive yellow and black markings on the abdomen and a mostly white cephalothorax. Its scientific Latin name translates to "gilded silver-face". The body length of males range from 5–9 mm (0.20–0.35 in); females range from 19–28 mm (0.75–1.10 in). These spiders may bite if disturbed or harassed, but the venom is harmless to non-allergic humans, roughly equivalent to a bumblebee sting in intensity.

<i>Argiope argentata</i> Species of spider

Argiope argentata, commonly known as the silver argiope or silver garden spider due to the silvery color of its cephalothorax, is a member of the orb-weaver spider family Araneidae. This species resides in arid and warm environments in North America, Central America, the Caribbean and widely across South America. In the United States, it is found at least in Southern California, Florida, Arizona, and Texas. A. argentata create stabilimenta and a unique zig-zag in its web design, and it utilizes its UV-reflecting silk to attract pollinating species to prey upon. Like other species of Argiope, its venom is not harmful to humans; however, it can be employed to immobilize its prey. A. argentata engages in sexual cannibalism either mid- or post-copulation. One aspect of particular interest regarding this species is its extinction patterns, which notably have minimal correlation with its population size but rather occur sporadically for the species.

<i>Gasteracantha fornicata</i> Species of spider

Gasteracantha fornicata is a species of spiny orb-weavers found in Queensland Australia. It is similar in shape to Austracantha minax which was originally described as Gasteracantha minax. It was described by Johan Christian Fabricius in 1775, the first Australian species of spider to be named and classified.

<span class="mw-page-title-main">Sexual cannibalism</span> Practice of animals eating their own mating partners

Sexual cannibalism is when an animal, usually the female, cannibalizes its mate prior to, during, or after copulation. It is a trait observed in many arachnid orders and several insect and crustacean clades. Several hypotheses to explain this seemingly paradoxical behavior have been proposed. The adaptive foraging hypothesis, aggressive spillover hypothesis and mistaken identity hypothesis are among the proposed hypotheses to explain how sexual cannibalism evolved. This behavior is believed to have evolved as a manifestation of sexual conflict, occurring when the reproductive interests of males and females differ. In many species that exhibit sexual cannibalism, the female consumes the male upon detection. Females of cannibalistic species are generally hostile and unwilling to mate; thus many males of these species have developed adaptive behaviors to counteract female aggression.

<i>Trichonephila plumipes</i> Species of spider

Trichonephila plumipes, the Pacific golden orb weaver, is a species of spider found in Australia, Indonesia and some Pacific Islands, which exhibits extreme sexual dimorphism through its sexual cannibalism behavior. It is sometimes called the tiger spider due to its markings which look similar to a tiger. This species was formerly called Nephila plumipes. As with other spiders from the genus Nephila, these spiders have a distinct golden web.

<i>Argiope pulchella</i> Species of arachnid

Argiope pulchella is a species of the orb-weaver spider family, Araneidae. It ranges from India to China and can be found on Java. It is a synanthropic species, often living in habitats associated with humans.

<i>Pisaurina mira</i> Species of spider

Pisaurina mira, also known as the American nursery web spider, is a species of spider in the family Pisauridae. They are often mistaken for wolf spiders (Lycosidae) due to their physical resemblance. P. mira is distinguished by its unique eye arrangement of two rows. 

<i>Tigrosa helluo</i> Species of spider

Tigrosa helluo is a species of spider belonging to the family Lycosidae, also known as wolf spiders. T. helluo was formerly known as Hogna helluo before differences between dorsal color patterns, habitat preferences, body structures, etc. were discovered. The species is native to the United States, Canada, and Mexico. It can be found across the eastern half of the United States, primarily in the Northeast and New England, and as far west as Nebraska and Kansas. T. helluo can be found in diverse habitats including woods, marshes, fields, and riparian areas. Typically, members of this species prefer to live in wetter areas as opposed to dry environments. Males tend to live for around a year and females will live for close to two years.

<i>Cyclosa argenteoalba</i> Species of spider

Cyclosa argenteoalba, in the trashline orbweavers genus, is a species of orb weaver in the spider family Araneidae. It is found in East Asia in the countries of China, Japan, and Korea. C. argenteoalba are diurnal, which means they are active during the day. Each individual has a unique appearance due to their differences in the ratio of black to silver coloring on their abdomen. Spiders with less silver coloring are better at catching prey, since the silver is bright and warns their prey. They catch their prey by waiting in the hub of their web until their prey is close enough to catch. Parasitic larvae are often found attached to C. argenteoalba, and the larvae are able to manipulate the spider's behavior. Females are on average 2 mm longer in size than males. During mating, female genital mutilation is common in order to increase the fitness of the male. On their webs, they often attach silk "decorations" that are thought to deter predators. Relocating to a different place to build a new web occurs frequently until they find a location with a significant amount of prey.

Agelenopsis pennsylvanica, commonly known as the Pennsylvania funnel-web spider or the Pennsylvania grass spider, is a species of spider in the family Agelenidae. The common name comes from the place that it was described, Pennsylvania, and the funnel shape of its web. Its closest relative is Agelenopsis potteri.

<i>Argiope radon</i> Species of spider

Argiope radon is a species of orb web spider native to Australia. It is found in tropical areas of the Northern Territory, Western Australia and Queensland. It is commonly known as the Northern St Andrew's cross spider.

<i>Argiope versicolor</i> Species of spider

Argiope versicolor, the multi-coloured Saint Andrew's cross spider, is a species of orb-weaver spider found mostly in Southeast Asia, from China to Indonesia.

<i>Leucauge mariana</i> Species of spider

Leucauge mariana is a long-jawed orb weaver spider, native to Central America and South America. Its web building and sexual behavior have been studied extensively. Males perform several kinds of courtship behavior to induce females to copulate and to use their sperm.

<i>Larinia jeskovi</i> Species of arachnid

Larinia jeskovi is a species of the family of orb weaver spiders and a part of the genus Larinia. It is distributed throughout the Americas, Africa, Australia, Europe, and Asia and commonly found in wet climes such as marshes, bogs, and rainforests. Larinia jeskovi have yellow bodies with stripes and range from 5.13 to 8.70 millimeters in body length. They build their webs on plants with a small height above small bodies of waters or wetlands. After sunset and before sunrise are the typical times they hunt and build their web. Males usually occupy a female's web instead of making their own. The mating behavior is noteworthy as male spiders often mutilate external female genitalia to reduce sperm competition while female spiders resort to sexual cannibalism to counter such mechanisms. The males also follow an elaborate courtship ritual to attract the female. The bite of Larinia jeskovi is not known to be of harm to humans.

<i>Gea eff</i> Species of spider

Gea eff is a species of orb-weaver spider. It is found in Papua New Guinea. The arachnologist Herbert Walter Levi formally described the species in 1983. While it was still undescribed, Michael H. Robinson and colleagues reported on its courtship and mating behaviors. Gea eff has the shortest scientific name of any spider species.

References

  1. 1 2 "Taxon details Argiope aemula (Walckenaer, 1841)", World Spider Catalog, Natural History Museum Bern, retrieved 2016-05-07
  2. 1 2 3 4 5 6 7 8 9 Cheng, Ren-Chung, and I-Min Tso. “Signaling by Decorating Webs: Luring Prey or Deterring Predators?” Behavioral Ecology, vol. 18, no. 6, 2007, pp. 1085–1091., doi:10.1093/beheco/arm081.
  3. 1 2 3 4 5 Abrenica-Adamat, Liza, et al. “The Influence of Prey on Size, Capture Area and Mesh Height of the Orb-Web of the Garden Spider.” Egyptian Academic Journal of Biological Sciences, B. Zoology, vol. 1, no. 1, 9 July 2009, pp. 65–71.,
  4. ↑ "Argiope aemula description". India Biodiversity Portal. Retrieved 12 November 2018.
  5. 1 2 3 Sasaki, Takeshi; Iwahashi, Osamu (1995). "Sexual cannibalism in an orb-weaving spider Argiope aemula". Animal Behaviour. 49 (4): 1119–1121. doi:10.1006/anbe.1995.0140. S2CID   140208434.
  6. ↑ Newman, J. A. & Elgar, M. A. 1991. Sexual cannibalismin orb-weaving spiders: an economic model.Am. Nat.,138,1372–1395.
  7. ↑ Elgar, Mark A., et al. “Female Control of Paternity in the Sexually Cannibalistic SpiderArgiope Keyserlingi.” Proceedings of the Royal Society of London. Series B: Biological Sciences, vol. 267, no. 1460, 7 Dec. 2000, pp. 2439–2443., doi:10.1098/rspb.2000.1303.
  8. 1 2 Cheng, R C. “Insect Form Vision as One Potential Shaping Force of Spider Web Decoration Design.” Journal of Experimental Biology, 2010.
  9. 1 2 Wei Yeh, Chien. “Top down and Bottom up Selection Drives Variations in Frequency and Form of a Visual Signal.” Scientific Reports, 21 Apr. 2015.
  10. ↑ Spontaneous male death during copulation in an orb-weaving spider
  11. ↑ Foellmer, Matthias W. “Spontaneous Male Death during Copulation in an Orb-Weaving Spider.” Proceedings of the Royal Society B, 7 Nov. 2003.


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