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Tegenaria domestica, anyone ???
Posted by Reposted on August 16, 2004 at 09:10:29:|
In Reply to: Peter Parkers Spider - On C/bar News update posted by Non-Spider fan!!! on August 14, 2004 at 17:19:53:
In Europe, members of the genus Tegenaria are often called house spiders since they are common inhabitants of houses and adjacent vegetation. Only a single species of Tegenaria, T. chiricahuae, is native to the United States. It occurs in caves and other dark places in Arizona and New Mexico. The other six species of Tegenaria found in the United States are of European origin. They were probably introduced to this country very early through commerce. Three species occur in the Pacific Northwest.
Tegenaria domestica, the domestic house spider, is common in both the Northeast and the Northwest, while Tegenaria gigantea, the giant house spider, has been collected to date in the Pacific Northwest and in Winnipeg, Canada. Neither of these two species are known to cause serious bite reactions in humans (Fig. 6). T. gigantea has been encountered more frequently than T. agrestis in the last few years.
Tegenaria agrestis, the aggressive house spider, is one of the most common spiders found in houses in the Pacific Northwest. Although this spider was first reported from Seattle in 1930, it did not become common in the Pacific Northwest until the 1960s. In the Pullman-Moscow, Idaho area, it is clearly a prevalent spider in basements and in window wells of houses. It rarely climbs vertical surfaces and is usually found only on the ground or lower floors. We have called it the "aggressive house spider" because it bites with little provocation when cornered or threatened.
Sexually mature males and females are abundant from mid-summer (July) through fall.
During this period males tend to wander relatively long distances in search of females. Eggs are laid into a spherical silken sac spun by the female, usually in September or October in the Pullman area. The sac is then placed within or adjacent to the funnel, usually on the underside of a rock or other object. This sac is usually covered with a thin layer of soil, wood chips, or other debris, including prey. The debris coated sac then is often covered with another layer of silk. Eggs hatch the following spring. Most Tegenaria molt about 10 times over a span of 2 years before reaching sexual maturity. Immatures are commonly found wandering in the spring searching for web sites.
Investigations of aggressive house spider bites show the venom produces skin injuries, or lesions, similar to those produced by the brown recluse. Therefore, ulcerating lesions of this type occurring on humans in Washington, Oregon, and Idaho are probably due to bites by the aggressive house spider. Surprisingly, males are somewhat more venomous than females.
Bites commonly occur as a spider is squeezed against the body when a homeowner picks up a firewood log with a spider on it or when a spider is located in an article of clothing and is squeezed when the clothing is put on.
The initial bite is not painful. It has been described as producing a very slight prickling sensation. However, a small, insensitive, hard area appears within 30 minutes or less, and is surrounded by an expanding reddened area of 5—15 cm in diameter (2—6 inches) (Fig. 8).
Within 15 to 35 hours the area blisters. About 24 hours later the blisters usually break, and the wound oozes serum. A cratered ulcer crusts over to form a scab. Tissues beneath the scab may die and slough away. In some cases the loss of tissue may become so severe that surgical repair is needed. The fully developed lesion can vary from about 1/2 to 1 inch or more in diameter. Lesions may take several months to heal, and frequently leave a permanent scar (Fig. 9).
Systemic illness may or may not accompany the bite. However, the most common symptom is a severe headache, sometimes occurring within 30 minutes, usually within 10 hours, that does not respond to aspirin. The headache may persist for 2 to 7 days, and is sometimes accompanied by nausea, weakness, tiredness, temporary loss of memory, and vision impairment. The symptoms are similar to those experienced with migraine headaches. Bites by Tegenaria agrestis have not caused a death. In Europe, their area of origin, there are few records of bites by these spiders causing medical problems. However, a person bitten by one of these spiders should seek immediate medical treatment.
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