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Arachnology is the scientific study of spiders and their kin, with particular emphasis on the identification of new species, the study of their biology and how they interact with their environment. Humans have had a fascination with these organisms since ancient times, with many early societies having myths with prominent spider figures. The most prominent of these is the Greek myth of Arachne, where our corner of science gets its name from. Arachne, a Lydian woman gifted in the art of weaving, eventually challenged the goddess Athena to a weaving contest. She lost, and for her arrogance was turned into a spider. Other notable figures in spider mythology include the trickster-spider Anansi from African lore, Neith the ancient Egyptian goddess of war and weaving, and Iktomi, the great trickster and teacher of wisdom, of the Lakota people of North America.

Arachnids are not insects. They are as separate from insects as a tiger is from a turtle. The class Arachnida comprises over 100 000 species of invertebrate organisms, with four pairs of jointed-legs, two body segments (the cephalothorax and abdomen), and a pair of modified appendages called pedipalps. The class is divided into eleven orders, the most recognisable being the true spiders (Araneae) and scorpions (Scorpiones). Other orders are camel/sun spiders (Solifugae), ticks and mites (Acari), harvestmen (Opiliones), pseudoscorpions (Pseudoscorpiones), whip spiders (Amblypygi), whiptail scorpions (Uropygi) and some rarely seen and unknown organisms such as the micro-whipscorpions (Palpigradi), schizomizids (Schizomida) and ricinulids (Ricinulei).

Many of the above-mentioned groups rarely come into contact with people because of their small size, reclusive and cryptic nature, camouflage and/or habitat restrictions. Pseudoscorpions, for example, are very common even in urban environments, but are rarely noticed due to their tiny size and nocturnal habits. Others such as the micro-whipscorpions, schizomizids and ricinulids are restricted to high-moisture forests.

The first image most people form in their minds when asked what an arachnid is, is almost always that of a spider. These often misunderstood creatures are at the centre of many myths and urban legends. These have resulted in the average person killing them rather than appreciating their beauty. This almost universal fear has become so common that arachnophobia is now one of the top three phobias in the world, affecting between 3.5% and 6.1% of the world’s population. It is believed that arachnophobia originated in 10th century Europe where it was commonly believed that all spiders were deadly, carried disease, and their mere presence would result in misfortune. Luckily this is far from the truth. Some non-European cultures even hold spiders in high regard. For the Native Americans a spider brings good luck and is a symbol of wisdom, while in Papua New Guinea, Costa Rica, Cambodia and Venezuela tarantulas are often included in traditional dishes.

So far there are over 40 000 spider species known worldwide. The smallest in the world, the Samoan Moss Spider (Patu marplesi), is just 0.3 mm in length, while the largest leg-span goes to the Giant Huntsman Spider (Heteropoda maxima) from the caves of Laos with a leg-span of 30 cm. The title of heaviest spider in the world goes to the Goliath Birdeater (Theraphosa blondi), a tarantula from northern South America, weighing in at 175 g with a leg-span of about 28 cm.

Spiders in general are an integral part of the predator component of an environment, and play a vital role in the control of invertebrates. They employ a range of hunting techniques including webs, active searching and sit-and-wait ambush. Some specialised hunting strategies are also involved. Bolas spiders, members of the orb-weavers, swing a droplet of glue, laced with a female moth pheromone, on a length of webbing to lure and catch male moths. Ogre-faced spiders (family Deinopidae) build an expandable net out of silk and then sit and wait on an elevated surface for a prey item to wander below them. They then throw the net downward over the prey item, to capture it. Assassin spiders (family Archaeidae), on the other hand, have a modified cephalothorax and elongated fangs that they use to catch other spiders. Their elongated fangs keep the prey spider at a safe distance, minimising the risk of getting bitten themselves. Some species of jumping spiders have extensively modified bodies that mimic ants. They  also excrete a pheromone mimicking that of the prey species, such that they are seen as one of the colony.

Spiders, especially male spiders, also have a variety of ways in which they communicate with a potential mate. The different techniques are very similar to the roles of members in a musical band. Tarantulas have very poor vision and are mostly terrestrial borrowers. Males have to be careful when approaching a female’s burrow as she may mistake him for a potential meal. To prevent this, males will drum the ground outside the burrow with their pedipalps to signal their intentions. If interested, the female will exit her burrow to inspect the male before mating occurs. Male spiders of web-building species have a similar technique, though instead of drumming they pluck on the silken threads at the edge of a female’s web, much like plucking guitar strings. Plucking in a specific way alerts the female in the web to his presence and intention. Male jumping spiders, on the other hand, sing and dance for their females. Males stridulate to attract the attention of a female. Many males are also brightly coloured as jumping spiders have excellent depth of field and colour vision. Their males will often then dance for females, swinging their front legs and showing off their bright colours in the hope of winning a female’s approval.

A question that most arachnologists get asked a lot, is how venomous/poisonous a particular arachnid is. Firstly, just to clarify, arachnids are venomous. An easy way to remember the difference is, if you bite it and die, it is poisonous, if it bites you and you die, it is venomous. Most arachnids are not medically significant or dangerous to humans. This is mostly because of their small size, or venom that is ineffective against humans. For example, even though tarantulas are quite large and have powerful fangs (Goliath Birdeaters have 2 cm long fangs), their venom is often weak. Many myths also exist about spider lethality and this often complicates and exasperates the problem. Some people believe that camel spiders are deadly. This is untrue as camel spiders, which are solifugids and not real spiders, do not even possess venom glands. Also, they are not related to ants, despite looking a little like them.

There are nevertheless a few medically significant arachnids that you are likely to encounter in South Africa. Although not deadly, sac-spiders, violin spiders and button spiders should be avoided. Also, any scorpion with a thick, robust tail and tiny pincers may be seriously venomous. In South Africa, these scorpions belong mostly to the Buthidae family and can range from matchbox-sized Uroplectes species that can be found around your home (the sting of which is in effect comparable to a wasp sting) to the large Parabuthus species of arid regions, that possess venom potent enough to pose a serious health risk.

REFERENCES

Baerg, W.J. 1922. Regarding the habits of tarantulas and the effects of their poison. Scientific Monthly 14: 482-489.

Dippenaar-Schoeman, A. 2014. Field guide to the Spiders of South Africa. Pretoria: Lapa.

Leeming, J. 2003. Scorpions of Southern Africa. Cape Town: Struik.

Schultz, S.A. & Schultz, J.S. 1998. The tarantula keepers guide: comprehensive information on care, housing and feeding. Revised edition. New York: Barron’s Educational Series.

FibreWild! – Mount Olympus, Athena and Arachne.

https://www.fiberwild.com/ideas/mount-olympus-athena-and-arachne-oh-my/ (26.09.2017).

Antonio_Tempesta_Arachne-and-Athena

Athena (right) arguing with Arachne over challenging her to a weaving contest. (Illustration: Antonio Tempesta, www.wikipedia.org) 

Hubbardia-pentapeltis

A rare and reclusive schizomizid spider (Hubbardia pentapeltis). (Photo: M. Hedin, www.wikipedia.org)

A-tiny-pseudoscorpion

A tiny pseudoscorpion on a human finger. Quite common, but rarely seen because of their small size and nocturnal nature. (Photo: J.A. Neethling)

The-Giant-Huntsman-spider

The Giant Huntsman Spider (Heteropoda maxima) from Laos. It possesses the largest leg-span (30 cm) of all spiders. (Photo: Petra and Wilfried, www.wikipedia.org)

A male Peacock spider

A male peacock spider (family Salticidae) performing a courtship dance. (Photo: J. Otto)

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