December 15, 2008

Huntsman spider

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Huntsman spider is a common name given to the family Sparassidae (formerly Heteropodidae). The larger specimens of these spiders are sometimes referred to as Wood Spiders, due to their common preference for inhabiting woody places (forest, mine shafts, woodpiles).

These eight-eyed spiders are found in Australia, New Zealand, South Africa, Southeast Asia, the Mediterranean, Florida, and Hawaii, and possibly in many other tropical and semi-tropical regions. They can be found as far north as England, Sweden and Wales .

Appearance

While frequently very large – in Laos, Heteropoda maxima males can attain a legspan of 250–300 mm (9.8–11.8 in) – Huntsman spiders are not deadly to humans. They do bite if provoked, but the victim will suffer only minor swelling and localized pain, and will recover in a day or two. Some larger types resemble tarantulas, and may be mistaken for them, as the Huntsman is related (which is why the term "Australian tarantula" has sometimes been used to describe them by the Natural History Museum in Sydney). Huntsmen can generally be identified by their legs, which, rather than being jointed vertically relative to the body, are twisted such that the legs extend forward in a crab-like fashion.

Many Huntsman spiders are dull shades of brown or grey. Their legs are covered with fairly prominent spines, but the rest of their bodies appear smooth. They are frequently found in sheds, garages and other infrequently-disturbed places. The Banded Huntsman (Holconia) is larger and grey to brown with striped bands on its legs. The Badge Huntsman (Neosparassus) is larger still, and brown and hairy. Its bite will inflict the worst injury, and local swelling and pain may cause nausea, headache, vomiting and heart palpitations. The tropical or Brown Huntsman (Heteropoda) is also large and hairy, with mottled brown, white and black markings. The eyesight of these spiders is not nearly as good as that of the Salticidae (jumping spiders). Nevertheless, their vision is quite sufficient to detect approaching humans or other large animals from some distance.

Habitat and distribution

Members of the Huntsman family of spiders are very common in Australia, but also in many tropical and semi-tropical parts of the world. They have been introduced to many parts of the world, including China, Japan and southern parts of the United States, such as Florida and Puerto Rico. A species of Huntsman can be found in Hawaii, where it is commonly known as a Cane Spider. In general they are likely to be found wherever ships may bring them as unintended passengers to areas that are not too cold for them to survive in the winter. In southern Africa they are commonly known as rain spiders because of their tendency to seek shelter before rain storms, often entering human habitations when doing so.[1][2]

As adults, Huntsman spiders do not build webs, but hunt and forage for food: their diet consists primarily of insects and other invertebrates. They live in the crevices of tree bark, but will frequently wander into homes and vehicles. They are able to travel extremely fast, and walk on walls and even on ceilings. They also tend to exhibit a "cling" reflex if picked up, making them difficult to shake off and much more likely to bite. The females are fierce defenders of their egg sacs and young. They will generally make a threat display if provoked, but if the warning is ignored they may attack and bite.

Toxicity and aggression

In general, Huntsman spiders are not regarded as dangerous, and can be considered beneficial because they feed on insects (Many Australians will relocate Huntsmen to the garden rather than kill them). There have been reports of members of the genus Neosparassus (formerly called Olios) giving bites that have caused prolonged pain, inflammation, headache, vomiting and irregular pulse rate; however, a scientific study into the bite of these spiders did not note any severe or unusual symptoms resulting from confirmed Neosparassus bites.[3] It is unclear under what circumstances these spiders bite people, but it is known that female members of this family will aggressively defend against perceived threats to their egg sacs and their young.

Sound production in mating rituals

Males of Heteropoda venatoria, one of the Huntsman spiders that seems to easily find its way around the world, have recently been found to deliberately make a substrate-borne sound when they detect a chemical (pheromone) left by a nearby female of their species. The males anchor themselves firmly to the surface onto which they have crawled and then use their legs to transmit vibrations from their bodies to the surface. Most of the sound emitted is produced by strong vibrations of the abdomen. The characteristic frequency of vibration and the pattern of bursts of sound identify them to females of their species, who will approach if they are interested in mating.[4]

Gallery

Genus Heteropoda

Genus Micrommata


Source: Wikipedia

1 comment:

News Review said...

Probably a great choice to become a pet.. Since its not harmful to humans..