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Many spiders are harmless, but a few are known to be more than a pesky visitor. Read on for some quick facts to help in identifiying some of the more dangerous spiders common in the Northwest and Southwest regions.

Hobo Spiders

Hobo Spider Facts

The Hobo Spider, Tegenaria agrestis, is a moderately large spider of the family Agelenidae which is indigenous to western Europe that was introduced into Hobo Spiderthe northwestern United States (Port of Seattle) sometime before the 1930's. The Hobo Spider (photo) is found from southern Alaska to central California and east into Colorado . Some individuals have found Hobo Spiders in the midwest and in the east, but this has not been confirmed.

In its native Europe the hobo spider is a resident of fields, rarely entering human habitations due to the presence of major competitors, particularly the giant house spider, Tegenaria gigantea , which is a common resident of houses and other man-made structures in Europe ; thus, human contacts with the hobo spider are uncommon in Europe .

The hobo spider, is a member of the family of spiders known as the Agelenidae or funnel web weavers . Approximately 500 species of funnel web weavers occur worldwide; about 300 of these are found in North America , and about 100 species are native to Europe . Funnel web weavers are characterized by their ability to move rapidly, and by their layered, flat web (photo) which has a funnel-like lair at the rear in which the spider resides and waits for prey. The web is not sticky like that of many spiders, but rather is a trip web , which traps insect prey that is unable to navigate on the surface.

Hobo spiders have been found in rural areas, including some heavily farmed areas. This is more like its European relatives.

Hobo Spider Breeding

Hobo Spiders appear to have a three-year life cycle. The eggs of the hobo are deposited in one to four egg cases in late September and October. These egg cases are composed of several layers of silk, intermingled with layers of soil and debris. The egg cases are usually attached to the undersides of rocks, wood, or other items found in yards, gardens and vacant lots; each egg case might contain 100 or more eggs. Female Hobos mostly lay their eggs outside, but can lay their eggs in houses, under the right conditions. The small spiders emerge, feed, and largely remain beneath the surface during their first season, molting their exoskeleton periodically as they grow. The juvenile spiders then overwinter, and are frequently found indoors during this period. During the early spring these young spiders appear to be very venomous and can cause some of the worst bites.

The females build webs and remain stationary, butHobo Spider Bite the males began nocturnal wanderings in search of mates. It is at this juncture that males enter houses (often in large numbers) from outside habitat and from garages and crawl spaces; thus, they come into contact with humans; most bites occur during this time period. The hobo spider season peaks during the first week or two of September in most areas. After mating the males began to die, and are absent by the first week of October. The females construct the egg cases, and most remain in the web until they die, usually expiring by mid-November: Some adult females do enter houses in late September, October, and November.

Hobo Spider Behavior

The behavioral aspects of the hobo spider have been a subject of controversy in the past, primarily due to the the publicized myth of the "aggressive house spider". While the hobo will bite when pressed against skin or tormented, it is no more "aggressive" than other wandering spiders; it does not bite without clear provocation, and certainly does not track people down and attack them, as some people have come to believe. The quick movements of this spider, and the fact that they sometimes run toward individuals when disturbed have fueled such myths, but the idea that such spiders are "attacking" is a misinterpretation. In actuality, these spiders have very poor vision and cannot distinguish objects more than a foot or two away. When disturbed inside a house, particularly when a light has just been turned on, the spiders most often remain stationary. When such spiders finally sense potential danger, they run, sometimes toward a person that they really can't see or, as it has been observed, run towards a person's shadow. Hobo spiders are not good climbers, and are usually found at ground or basement level. They sometimes climb up to a level of about four feet if the surface of the wall, etc. is sufficiently porous. Hobo spiders found in wash basins and bathtubs arrived there by falling down the slick porcelain surface; they did not come up through the drain.

Hobo Spider Characteristics

Physically, the adult hobo spider is a moderately large (12-18 mm body length) brown spider, with long, unmarked legs (legs included, a typical specimen would fit nicely on a silver dollar). The dorsal abdomen exhibits a "herringbone" or multiple chevron pattern, which may be quite obscure in darker individuals. The male sports two pedipalps (antennae like protuberances) between the two front legs, which are swollen at the ends, looking somewhat like a pair of boxing gloves; these "boxing gloves" are actually the male genitalia, not "fangs" or "poison sacs". The female generally has a larger abdomen than the male, and does not have swollen "boxing gloves" at the ends of the pedipalps. Several other spiders resemble hobo spiders; only an arachnologist, or other specifically trained person should attempt to make a positive identification of this species: In an instance where a spider has bitten a person, it is imperative to obtain positive identication only from a qualified professional arachnologist.

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Brown Recluse Spiders

Brown Recluse Facts

Brown Recluse Spiders are very abundant poisonous species of spider in many states. The spiders vary in size and coloration, their definitive marking is a dark, violin-shaped pattern on the front part of the spider’s back that stands out against a lighter background that matches the coloration of the legs. The brown recluse is common in homes and other structures throughout the natural distribution area in the central and southern United States. The spider feeds on insects. When weather conditions are adequate for insects to do well they come in the house and the spiders follow.

The best way to avoid being bitten is to make your home unwelcome to the brown recluse. The spiders prefer dark tight spaces, so it is a good idea to seal cracks and clear out clutter. Glue traps can be purchased at grocery and hardware stores and are useful in determining how serious an infestation is.

Most insecticidal products are ineffective against the brown recluse unless the spiders are sprayed directly. If you are bitten by a brown recluse experts recommend applying an icepack to the bite and bringing the spider to the doctor’s office in aiding the identification of the spider.

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Yellow Sac Spiders

Yellow Sac Facts

Sac spiders are moderately small, yellowish colored spiders that prefer to live among plants, but are often found in houses in many areas of the United States. They are often transported into Northwestern states in clusters of grapes from vineyards in California and elsewhere. These spiders are probably actually responsible for most “brown recluse” bites reported in certain parts of the country.

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Black Widow Spiders

Black Widow Facts

Female black widow spiders are 12-16 mm in length, with black shiny abdomens that exhibit a red “hourglass” or similar pattern on the underside. Black widow spiders are secretive, almost blind, and spend most of their lives in the web, which is often built in dark corners, window wells, and well housings.

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