Of the 35,000 species of spiders described worldwide (out of an estimated 170,000 species), only a handful are considered to be dangerous and only 27 are known to have caused human fatalities.
Though most people have a big fear of spiders, it seems that venomous spiders are not such a big threat to humans as many people believe.
First of all, studies have shown that most serious bites attributed to spiders were, in fact, due to other causes, notably other arthropods.
Secondly, antivenin against spider bite has become very effective and thus made the occurrence of death resulting from a spider's bite a very rare thing.
Lastly spider venom, in general, is usually almost harmless to humans, since it evolved for capturing or killing small invertebrates and not big mammals like ourselves.
There are, however, a few exceptions, and bites from certain species can cause severe dermatological lesions and other symptoms which require urgent medical treatment and care.
The spiders of medical importance in Asia include widows and cupboard spiders (also called Brown House spiders or False Widows, family Theridiidae) which venom may contain neurotoxins responsible for serious systemic envenomation.
Though not especially venomous, a number of Asian tarantulas can also be regarded as potentially dangerous.
1. Widows (Latrodectus)
The name widow originates from the idea that the male is eaten after mating but this is uncommon in the field.
The genus Latrodectus contains around thirty described species and belongs to the large family Theridiidae. Black and Brown Widows occur on all continents, except Antarctica and are mostly common in tropical and sub-tropical regions.
The female spider is 12-16 mm long while males are 4 to 5 times smaller.
Widows are active during the day and rarely come indoors. The female spins a messy three-dimensional web in protected corners of fields, gardens, near stones and woodpiles and in vegetation, in which she hangs upside down. The male spider does not produce a web and is not considered dangerous for humans.
Bites of the females of Latrodectus are often initially painful but are also sometimes not felt. In 50% of hospitalized cases, a severe pain lasts from one to three days. The use of antiserum may shorten the duration of the symptoms but is usually not required. Analgesics, myorelaxants and calcium gluconate are used to relief the symptoms.
The fear for this spider, often considered deadly is, however, exaggerated. Indeed, since 1954 it hasn't been responsible for any fatal bite cases in Australia, nor since 1983 in the USA, and there has never been a reported death by these spiders in the rest of the world. Besides, Widows are not aggressive spiders.
- Latrodectus dahli: found from the Middle East to central Asia.
- Latrodectus elegans: found in China, Myanmar, Thailand, Japan.
A Brown widow spider very common in Thailand, where it likes to settle inside garages and other human structures. It is shy and not very likely to bite, however it has a strong neurotoxic venom and can be dangerous, especially for young children.
- Latrodectus erythromelas: found in Sri Lanka.
- Latrodectus hasselti: found in southeastern Asia, Australia, New Zealand.
- Latrodectus hystrix: found in Yemen, Socotra.
- White Widow, White Steppe Spider (Latrodectus pallidus) : found in the Middle East, Iran and Russia (as well as North Africa and Cape Verde).
- Latrodectus revivensis: found in Israel.
- Mediterranean Black Widow, European Black Widow (Latrodectus tredecimguttatus): found in central Asia, Kazakhstan and China (as well as the Mediterranean area).
2. Sac Spiders (Cheiracanthium)
Family Miturgidae (previously Clubionidae)
The nearly 200 species described in this family are thought to be beneficial predators in agriculture.
- Yellow Sac Spider (Cheiracanthium punctorium)
Cheiracanthium punctorium is found from central Europe to Central Asia; it is especially common in the Central Asian steppes. It prefers fairly hot and arid areas.
It can measure up to 15 mm and, like other members of the Miturgidae family, it has a long first pair of legs and stout fang. Those fangs can penetrate the human skin causing a sharp pain that commonly last for twelve hours, and in some cases for as long as ten days.
The bite is similar to a wasp sting, perhaps a bit more severe, although susceptible persons can have stronger reactions, like nausea and, rarely, necrosis of the skin.
Females build an egg sac of about 4 cm in high grass. It opens below and is aggressively defended.
- Cheiracanthium japonicum: found in Japan.
3. Tarantulas
Contrary to popular belief, tarantulas are venomous, like most spiders. No one has ever died from a bite of a tarantula though.
The potency of the venom depends on the kind of tarantula. Tarantulas from the new world (Americas) have the no worse than bee sting venom. Instead though, they can kick hair off their legs and abdomen which can cause bad rashes.
Old world tarantulas (Asia, Middle East, Africa) are usually more aggressive, have a much stronger venom, and may require medical attention (especially for the Poecilotheria and Haplopelma genus).
3.1 Poecilotheria
Poecilotheria is a genus of the family Theraphosidae containing various species of arboreal tarantula.
Poecilotheria spiders are native to Sri Lanka and India.
They have vivid color patterns on their abdomens.
In the wild, most arboreal tarantulas live in holes of tall trees where they make asymmetric funnel webs. They prey mostly on various flying insects, which they catch manually (not in a web) and paralyze. Poecilotheria spiders sometimes live communally, especially when the availability of tree holes is limited.
Poecilotheria are very fast and may attack when cornered, although they generally prefer flight to fight.
Although there has never been a recorded death from any tarantula bite, Poecilotheria species have a more potent venom than most other tarantulas and their bite, which causes an intense pain is considered to be medically significant.
Poecilotheria species are:
- Gooty Sapphire Ornamental Tree Spider, Gooty Sapphire.
(Poecilotheria metallica)
Found in the southeastern part on India and in Sri Lanka. The name "Gooty" comes from the town where this species was first discovered.
This metallic blue tarantula likes hot humid environments. Its leg span measures between 15 and 20 cm (6- 8 inches). Females can live for about 12 years, males only for 3 or 4.
The Gooty Sapphirre is a favorite with tarantula enthusiasts and adult specimens can price above $500 in the USA.
- Poecilotheria fasciata: found in Sri Lanka
- Poecilotheria formosa: found in India
- Poecilotheria hanumavilasumica: found in India
- Poecilotheria miranda: found in India
- Poecilotheria ornata: found in Sri Lanka
- Poecilotheria pederseni: found in Sri Lanka
- Indian Ornamental Tree Spider, Indian Ornamental (Poecilotheria regalis): found in the southeasten parts of India. Their leg span can exceed 18 cm (7 inches).
- Poecilotheria rufilata: found in India
- Poecilotheria smithi: found in Sri Lanka
- Poecilotheria striata: found in India
- Poecilotheria subfusca: found in Sri Lanka
- Poecilotheria tigrinawesseli: found in Sri Lanka
- Poecilotheria uniformis: found in Sri Lanka
3.2 Haplopelma
This genus of old-world tarantulas are found in the rain forests of southeast Asia: Myanmar, southeastern China, Cambodia, Thailand, Vietnam, Malaysia, Singapore, and Borneo. They need humidity levels of up 70% or more.
These large spiders typically have leg spans ranging from 13 to 20 cm (4.5 to 8 inches).
Haplopelma spiders live in burrows they build up several feet deep, emerging to capture prey (mostly insects such as co*ckroaches and crickets, but also mice).
Like all old-world tarantulas, the Haploplema spiders lack the urticating hairs of their new world counterparts, and use biting as a primary means of defense. They are reputed to have a bad temper and are likely to bite when handled. Old world tarantulas are known for having strong venom (but the venom of many species still has to be studied)
Species in Haplopelma include:
- Chinese Bird Spider, Black Earth Tiger (Haplopelma hainanum, Haplopelma schmidti)
This species of tarantula is native to many parts of Asia, notably the tropical rain forests of China and Vietnam.
This jet black spider is huge: its leg span can reach up to 20 cm (8 inches).
Although the Chinese Bird normally preys on insects and small rodents, this fearsome and extremely aggressive species will not hesitate to bite a human being, often attacking without provocation.
This aggressive nature, backed by an incredible speed and very large fangs, have led to this species being considered one of the most dangerous spiders in the world.
A small dose of the Chinese Bird's venom, which attacks the nervous system, and is fatal to laboratory rats and mice.
- Thailand Black Tarantula, Bird Eating Spider (Haplopelma minax)
This spider occurs in Myanmar and Thailand where it is quite common in gardens (and far less so inside houses). A fully grown female can reach 10 cm (4 inches). This tarantula is venomous, but not too potent, though it can cause a bad reaction, notably in children.
- Cobalt Blue Tarantula (Haplopelma lividum)
Found in Myanmar and Thailand.
It is known to sprnd most of its time inside its underground burrow.
Like most Asian tarantulas, it is very aggressive and possesses a painful, dangeous bite.
- Thai Zebra Tarantula (Haplopelma albostriatum), also known as the "edible spider": found in Myanmar, Thailand, Cambodia.
- Haplopelma doriae: found in Borneo (Indonesia)
- Haplopelma longipes: found in Thailand and Cambodia.
- Malaysian Blue-Femur Earth Tiger (Haplopelma robustum): found in Singapore.
- Haplopelma salangense: found in Malaysia.
- Haplopelma vonwirthi: found in southeastern Asia.
Sources:
http://www.entomon.net/venomous-most-deadly-spiders-kevlar-webs.htm
Venomous and Most Deadly Spiders
http://venomous-spiders.nanders.dk/
Venomous spiders - poisonous spiders
http://spiders.ucr.edu/dermatol.html
Bites and Stings of medically important venomous arthropods
Richard S. Vetter and P. Kirk Visscher
Department of Entomology, University of California
Published in the International Journal of Dermatology, volume 37, page 481-496, July 1998
http://en.wikipedia.org/wiki/Latrodectus
Latrodectus
http://www.entomon.net/framed-black-insect-spider-from-asia.htm
http://my.funtrivia.com/submitquiz.cfm?quiz=261121
http://www.thaivisa.com/forum/Spiders-Thailand-t69841.html
http://answers.yahoo.com/question/index?qid=20080720170839AAGTL3S
Are Tarantulas Poisonous?
http://www.ncbi.nlm.nih.gov/pubmed/12165044
Spiders of medical importance in the Asia-Pacific: atracotoxin, latrotoxin and related spider neurotoxins.
Nicholson GM, Graudins A.
http://en.wikipedia.org/wiki/Poecilotheria_metallica
http://en.wikipedia.org/wiki/Poecilotheria_regalis
Poecilotheria regalis
Family: Theraphosidae
http://en.wikipedia.org/wiki/Poecilotheria
http://en.wikipedia.org/wiki/Ornithoctoninae
http://en.wikipedia.org/wiki/Haplopelma
http://en.wikipedia.org/wiki/Cobalt_blue_tarantula
http://en.wikipedia.org/wiki/Cheiracanthium_punctorium
