Orb-web spiders in Fish Hoek garden – the banded argiope & Tropical tent-web spider

The yellow and black Common banded argiope, Argiope australis, in Fish Hoek garden. Photo by Karen LarsenWe have two orb web spiders that have made their home in our pavement garden on the mountainside in Fish Hoek, stringing their webs out between aloes and lavender bushes at about knee-height. Just alongside the big neat web of the yellow and black Common banded argiope, Argiope australis, is the multifaceted web of a female Cytophora citricola or Tropical tent-web spider. Both spiders belong to the family Araneidae (orb-web spiders) and both are harmless.
The webs of Argiope spiders are large and have two zigzag strands of silk running from the centre to the corners of the web, known as stabilimenta. As with other diurnal spiders the webs are kept in place for several days with the spider making running repairs when necessary. As it dries the web becomes less sticky and less capable of catching prey. Nocturnal spiders rebuild their webs every night, dismantling and eating it at dawn thus recycling the silk. The webs of the family Araneidae “occupy a niche utilized by few other spiders” – the airy spaces between bushes and trees in the flight path of other insects. (The Nephilidae also occupy this space)

 

The yellow and black Common banded argiope, Argiope australis, in Fish Hoek garden. Photo by Karen Larsen The female Argiope spends her time hanging head down in the centre of her web, her two pairs of forelegs held together and stretched out forwards mirrored by the hind two pairs stretching out backwards, forming an X.

 

Argiope approaches her prey ensnared in the web, turns and spins sheets of silk thread around it with her hind legs. The prey is then eaten through the silk wrapping after it has been immobilised with venom. The internal organs of the prey are turned into a “soup” with the enzymes pumped into it via the mouth of Argiope, as spiders cannot eat solids. If the spider is not hungry it will carry the prey to the edge of the web and leave it there till hungers strikes.

 

The yellow and black Common banded argiope, Argiope australis, in Fish Hoek garden. Photo by Karen LarsenThe adult female, as pictured in these photographs, grows to 25 mm and has a leg span of  85 mm. The male, about a thousandth of her weight, is only about 5.5 mm, with a leg span of up to 18 mm.

 

The male spider sneaks up on the female to mate, once mated he retreats quickly before she eats him! Unlike the very obvious egg sacs of the tent spider, the Common banded argiope’s egg sacs are heart-shaped and camouflaged. Up to 1000 eggs are laid but only 2% survive to become adult spiders .Young spiders are cannibalistic thus forcing the other spiders to disperse.

 

Cytophora citricala,  the tropical tent spider. Image from GoogleOnly one species of Cytophora has been identified in southern Africa. “Their distinctive web is a globe of criss-crossed, tangled threads… with a horizontal or near- horizontal fine orb web (in the centre)… pulled up slightly at the hub to form a tent-like sheet”.  The spider hangs under the web awaiting its prey which falls from the tangled threads into the central orb web, where it is rendered motionless by venom. The web of this spider is not sticky.

 

Cytophora citricola varies in colour from brown to black to speckled black and white. The females resemble a piece of dead leaf and many females may build their webs near to one another, forming large colonies. Males die soon after mating, and the females may die before their young are hatched. Their eggs sacs, of which there may be up to 10 in number,are up to 20mm long.

 

Egg sacs of Cytophora citricola, the tropical tent spider, in Fish Hoek garden. Photo Viv von der HeydenIn the accompanying photo of the web of the tropical tent spider, you will see its egg sacs and the remains of prey. The spider camouflages itself below the sacs and, when disturbed drops into the surrounding vegetation, instantly turning black, to camouflage itself. Cytophora citricala is both diurnal and nocturnal.

 

Quoted information comes from the book, Filmer’s Spiders An Identification Guide for Southern Africa by Martin Filmer and revised by Norman Larsen.

 

My grateful thanks to Karen Larsen for her lovely photos and to  Mark Hawthorne and to Norman Larsen (Associate Arachnologist,  Iziko, South African Natural History Museum) for their help in identifying the spiders. Norman very kindly verified the facts in this article and provided  additional information. He is available to give talks to interested groups. Email him on avellopsis@telkomsa.net

http://www.biodiversityexplorer.org/

See also http://scenicsouth.co.za//2012/03/golden-orb-web-spider-a-large-garden-spider-of-the-south-peninsula-cape-town/

Filmer's Spiders - An identification Guide for Southern Africa by Martin R Filmer. Revised by Norman Larsen

Out of interest I decided to Google “spiders in African folktales and mythology” . This is what I found….

 

Spiders in African folk lore

 

In African mythology the spider is personified as a creation deity Anansi and in traditional folklore as a trickster who can change is image to look like a human, a fox and other animals The name Anansi has been anglicised in parts of the America and in the West Indies as Aunt Nancy in allegorical tales that teach moral lessons.

 

The most well known storyconcerning spiders in African mythology is the ancient story of Anansi from West Africa, which has many variations. The most common variation teaches the moral of not being greedy, for Anansi tied his legs to webs so that he could be near a variety of pots of food. When he tried to pull away, his legs elongated and became very thin. Apart from being a fable illustrating punishment for greed, it also “explains” why spiders’ legs are so thin.

 

In a well-known story depicting Anansi as a trickster, he promised God that he would repay him with 100 servants if he, God, gave him and ear of corn. Taking the ear of corn to a village he tells the people that it is sacred. During the night he feeds the corn to the chickens and in the morning he accuses the villagers of stealing the missing corn. They give him a bushel in return. Tricking various people in a number of villages he manages in this manner to exchange the corn for a chicken, the chicken for sheep, the sheep for a corpse which he tells his next victims that it is the sleeping son of God. When they cannot awaken the corpse the next morning, Anansi accuses them of having killed the son of God, Terrified, they offer him 100 fine men whom Anansi takes to God to fulfil his side of the bargain.

 

Nyiko is a god spider who dropped out of the sky to live in the grasslands of Cameroon when he was kicked out of the family web by his father who accused him of having ‘evil relations’ with his mother.

Neith is a goddess in Egyptian mythology that represents the moon but often takes the shape of a spider. She represents hunting and is s seen also as the goddess of war.

 

Resources:

www.tribes.tribe.net

http://www.ehow.com