Red-back spider
|
|
| Red-back spider | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Missing image Redback.JPG Red-back spider Red-back spider | ||||||||||||||
| Scientific classification | ||||||||||||||
| ||||||||||||||
| Binomial name | ||||||||||||||
| Latrodectus hasselti Thorell, 1870 |
The red-back spider (Lactrodectus hasselti) is a potentially dangerous spider now found throughout Australia. Its origins are uncertain, and it may have been spread by human activities during the 19th century. Red-back spiders are now found in all but the most inhospitable environments in Australia, particularly in urban and suburban areas.
The red-back spider is related to the black widow spider (Lactrodectus mactans) found in North America and other regions but is smaller. Closer relatives are the katipo (Latrodectus katipo) and black katipo (Latrodectus atritus) spiders native to New Zealand. The female red-back has a round body about a centimeter long, with long, slender legs. The body is a deep black colour, often (but not always) containing a red line or small red dots on the abdomen. The male red-back is three to four millimeters long and is light brown in colour with white markings on the upper side of the abdomen. A related species is the brown widow spider, first located in Brisbane, Australia in 1987.
A successful bite from a female red-back injects a neurotoxin into the blood stream. Individuals bitten often describe the bite as extremely painful. Despite this (and in contrast to common belief in Australia) deaths from the red-back have been rare: A single death has been reported since the introduction of antivenin in 1956. It is, however, recommended to seek medical attention following a bite. This is particularly true for children, the elderly or those with serious medical conditions since the bite could be much more life threatening to these groups.
Contrary to common belief, bites from male red-back spiders are also occasionally dangerous, as reported by the Queensland Museum. About 250 people are bitten each year across Australia. Since the female red-back is slow moving and rarely leaves its web, most bites occur as a result of a person placing a hand or other body part too close to the web, such as reaching into dark holes or wall cavities.
Most Australians dislike the red-back spider, even more than other dangerous spiders, thanks in part to the frequency with which it is encountered in the environs of human habitations (it managed to secure a footing in Australian folklore in 1972 when it was immortalised in the song 'Redback on the Toilet Seat' by Ralph Newton). In reality it is far less dangerous to the general population than a number of other dangerous spider species native to Australia.
In September 2004, inmates at Grafton maximum security prison in New South Wales were found to be keeping red-back spiders in a jar. Worldwide media reported a prisoner's allegation that other inmates had been breeding the spiders, milking them, and injecting the venom for a high. However, the authorities uncovered no supporting evidence (e.g. syringes), and concluded the spiders were kept simply as pets.
The red-back spider is one of only two animals to date where the male has been found to actively assist the female in sexual cannibalism. In the process of mating, the much smaller male somersaults to place his abdomen over the female's mouthparts. In about 2 out of 3 cases, the female consumes the male while mating continues, and if not, the male dies soon after mating. This strategy seems to benefit the male because the female will not mate again.
External links
- Australian Museum (http://www.austmus.gov.au/factsheets/redback.htm)
- Rochedale State School (http://www.rochedalss.eq.edu.au/spider/spider2.htm)
- Queensland Museum (http://www.qmuseum.qld.gov.au/features/spiders/redback-bg.asp)
- University of Toronto (http://www.scar.utoronto.ca/~mandrade/animals.htm)ja:セアカゴケグモ