The genusArgiope 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.[2] The carapaceofArgiope 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.[3]
Description
As with most orb weavers, they have a third claw which is used to weave their complex webs. There is significant sexual dimorphism among the various species, with females measuring 19mm-28mm (0.75”-1.1”) and males coming in at 5mm-9mm (0.20”-0.35”).[3] Their webs can be quite large, usually containing a signature zig-zag pattern, called a stabilimentum[4]. They sport black and yellow patterning on their abdomen, and occasionally on their legs,[5] although most species have black legs with red or yellow patterning closer to the body. Their cephalothorax is covered with short silver hairs, and they have an egg-shaped abdomen.[3]
Argiope bruennichi is commonly known as the wasp spider. In Australia, Argiope keyserlingi and Argiope aetherea are known as St Andrew's cross spiders, for their habit of resting in the web with paired legs outstretched in the shape of an X and mirroring the large white web decoration (the cross of St. Andrew[2] having the same form). This white zigzag in the centre of its web is called the stabilimentum or web decoration.[2]
In North America, Argiope aurantia is commonly known as the black and yellow garden spider, zipper spider, corn spider, or writing spider, because of the similarity of the web stabilimenta to writing.
The East Asian species Argiope amoena is known in Japanaskogane-gumo. In the Philippines, they are known as gagambang ekis ("X spider"), and gagambang pari ("priest spider", due to the spider's body resembling a priest's head with a mitre).
Web
The average orb web is practically invisible, and it is easy to blunder into one and end up covered with a sticky web. The visible pattern of banded silk made by Argiope is pure white, and some species make an "X" form, or a zigzag type of web (often with a hollow centre). The spider then aligns one pair of its legs with each of the four lines in the hollow "X", making a complete "X" of white lines with a very eye-catching spider forming its centre.
The zigzag patterns, called stabilimenta, reflect UV light.[2] They have been shown to play a role in attracting prey to the web, and possibly in preventing its destruction by large animals. The centres of their large webs are often just under 1 metre above the ground, so they are too low for anything much larger than a rabbit to walk under. The overtness of the spider and its web thus has been speculated to prevent larger creatures from accidentally destroying the web and possibly crushing the spider underfoot.
Other studies suggest that the stabilimenta may actually lead predators to the spider; species such as A. keyserlingi place their web predominantly in closed, complex habitats such as among sedges.
AsArgiope sit in the centre of their web during the day, they have developed several responses to predators, such as dropping off the web, retreating to the periphery of the web, or even rapidly pumping the web in bursts of up to 30 seconds, similar to the motion done by the unrelated Pholcus phalangioides.[6]
The male spider is much smaller than the female,[7] and unassumingly marked. When it is time to mate, the male spins a companion web alongside the female's. After mating, the female lays her eggs, placing her egg sac into the web. The sac contains between 400 and 1400 eggs.
These eggs hatch in autumn, but the spiderlings overwinter in the sac and emerge during the spring. The egg sac is composed of multiple layers of silk and protects its contents from damage; however, many species of insects have been observed to parasitise the egg sacs.
Bite
Like almost all other spiders, Argiope are harmless to humans. As is the case with most garden spiders, they eat insects, and they are capable of consuming prey up to twice their size. A. savigny was even reported to occasionally feed on the small batRhynchonycteris naso.[8]
They can potentially bite if grabbed, but other than for defense, they do not attack large animals. Their venom is not regarded as a serious medical problem for humans; it often contains a wide variety of polyamine toxins with potential as therapeutic medicinal agents.[9] Notable among these is the argiotoxin ArgTX-636 (A. lobata).
A bite by the black and yellow garden spider (Argiope aurantia) is comparable to a bee sting, with redness and swelling. For a healthy adult, a bite is not considered an issue.[10][11][12]
Though they are not aggressive spiders, the very young, elderly, those with compromised immune systems, or those with known venom allergies should exercise caution, just as one would around a beehive.[10]
Taxonomy
The first description of the genus Argiope is attributed to Jean Victoire Audouin in 1826,[1] although he wrote that the genus was established by Savigny.[13] In the first edition of the work in which the description appeared (Description de l'Égypte: Histoire Naturelle), Audouin used the spelling "Argyope", for both the French vernacular name and the Latin generic name.[13] In the second edition, he continued to use "Argyope" for the French vernacular name, but the first mention of the Latin generic name had the spelling "Argiope", although the binomial names of the species continued to use "Argyope".[14] This led to controversy as to whether Audouin had intended to correct the spelling of the generic name, which is derived from the Greek αργιόπη. In 1975, the International Commission on Zoological Nomenclature validated the spelling "Argiope", on the basis that the change from the first to the second edition was an intended correction.[15][16]
Species
As of April 2019[update], Argiope contains 88 species:[1]
A. levii Bjørn, 1997 – South Africa, Kenya, Tanzania
A. lobata (Pallas, 1772) – Southern Europe to Central Asia and China, northern Africa, South Africa, Israel, India, from Myanmar to New Caledonia and northern Australia
A. trifasciata (Forsskål, 1775) – North, Central and South America. Introduced to Africa (Egypt;[17] type locality), Portugal to Israel, Iran, China, Japan, Australia (Tasmania), Pacific Is.
Argiope use autotomy – restricting blood flow to their own leg until it falls off – to minimize blood loss due to injury.[18][19] This is triggered by pain.[18][19]Honeybee and waspvenoms induce the same pain in Argiope – even when the injury is minor – causing Argiope to drop the affected leg.[18][19] The same effect can also be produced by chemically fractionated components of those venoms (specifically serotonin, histamine, and phospholipase A2) that also cause pain in humans.[18][19]
^Strømgaard, K. & Mellor, I. (2004). "AMPA receptor ligands: Synthetic and pharmacological studies of polyamines and polyamine toxins". Medicinal Research Reviews. 24 (5): 589–620. doi:10.1002/med.20004. PMID15224382. S2CID24802888.
Craig, C.L.; Wolf, S.G.; Davis, J.L.D.; Hauber, M.E. & Maas, J.L. (2001). "Signal polymorphism in the web-decorating spider Argiope argentata is correlated with reduced survivorship and the presence of stingless bees, its primary prey". Evolution. 55 (5): 986–993. doi:10.1111/j.0014-3820.2001.tb00615.x. PMID11430658. S2CID221734793.
Blamires, Sean J.; Hochuli, Dieter F. & Thompson, Michael B. (2007). "Does decoration building influence antipredator responses in an orb-web spider (Argiope keyserlingi) in its natural habitat?". Australian Journal of Zoology. 55: 1–7. doi:10.1071/ZO06098.
Fromhage, L.; Uhl, G. & Schneider, J. (2003). "Fitness consequences of sexual cannibalism in female Argiope bruennichi". Behavioral Ecology and Sociobiology. 55: 60–64. doi:10.1007/s00265-003-0656-6. S2CID9215208.
