SPIDERS

Types: Hobo, Black Widow

Organism, mostly terrestrial, of the class Arachnida with four pairs of legs and a two-part body consisting of a cephalothorax, or prosoma, and an unsegmented abdomen, or opisthosoma. The cephalothorax is covered by a shield, or carapace, and bears eight simple eyes. On the underside of the head (the cephalic part of the cephalothorax) are two pairs of appendages, the anterior pair called chelicerae and the second pair pedipalps, with which the spider captures and paralyzes its prey, injecting into it venom produced in the poison glands. The spider then liquefies the tissues of the prey with a digestive fluid and sucks this broth into its stomach where it may be stored in a digestive gland. Breathing is by means of tracheae (air tubes) or book lungs , or both. Arachnid book lungs are similar to the gill books of horseshoe crabs but are internal and adapted to a terrestrial habitat. Three pairs of spinnerets toward the tip of the abdomen produce protein-containing fluids that harden as they are drawn out to form silk threads. Several kinds of silk glands and spinnerets produce different kinds of silk used variously for constructing cocoons or egg sacs, spinning webs, and binding prey; other light strands are spun out for ballooning, or floating, the spiders, especially young ones, long distances on air currents. Spider silk is used for the cross hairs in certain optical instruments. Spiders live chiefly on insects and other arthropods; some large spiders ensnare and kill small snakes, birds, and mammals. Many are cannibalistic; the female may eat the male when courtship and mating are completed. Young, growing spiders can regenerate missing legs and parts of legs. Several species of spiders have bites that are exceptionally painful, or even dangerous to humans. Species of black widow spiders, which are found in the warmer parts of the world including the United States and S Canada, have a virulent neurotoxic venom. The bite venom of the brown recluse spider of SE and S central United States decomposes tissue, resulting in slow healing and sometimes leaving a sunken scar as large as a quarter. Among the more interesting spiders are the tarantula ; its relative the trap-door spider , which ambushes its prey from a silk-lined burrow covered by a hinged lid; the orb weavers, which spin beautiful circular webs; and the crab spider, jumping spider, and wolf spider, named for their habits. Spiders are classified in the phylum Arthropoda , class Arachnida, order Araneae.

Hobo Spiders

Vary from ½" to 1 ¾" in body length, with dark brown carapace. The abdomen has a chevron pattern that often fades in older specimens. The hobo spider actually helps control many insect pests. During late summer the male travels about looking for mates. Hobo spiders bite when startled or threatened. What starts as a small spider bite can grow into a large wound as its powerful venom slowly kills the flesh. Hobo spiders spin a distinct, dense, funnel-shaped web, typically along foundations, in woodpiles, stacked equipment, or yard waste. The hobo spider rarely climbs high on vertical surfaces, so search low to the ground. Hobo spiders do not create all funnel-shaped webs, but treat them all carefully. Wear gloves when working in the yard, cleaning your basement, or reaching into dark areas. 

Hobo spiders or Brown Recluse?  Hobo spiders  belong to the family Agelenidae or funnel web weavers which is indigenous to western Europe that was introduced into the north western United States sometime before the 1930's. The Hobo spiders' introduction into the United States was almost certainly commercial shipping vessels from Europe, transported to and arrived in the Port of Seattle as egg cases attached to wood, etc., rather than as live spiders. Considering the seasonal nature of the Hobo Spider, it is highly unlikely that a viable breeding population would have developed in the United States based upon the occasional introduction of adult or juvenile spiders.

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; therefore, human contacts with the hobo spider are uncommon in Europe. In the United States however, the Hobo Spider rapidly adapted to living in urban areas, and without the widespread presence of a dominant competitor, became abundant and began to extend its range; by 1968 it had become established as far east as Spokane, Washington and Moscow, Idaho, and as far south as Corvallis, Oregon.

In the late 1960's and early 1970's physicians in Idaho , Oregon, and Washington were presented with cases of probable spider bite that closely resembled bites caused by the brown recluse spider, Loxosceles reclusa. Studies conducted between 1974 and 1982 suggested that another spider was probably the actual agent of these bites. Finally, in 1983, field studies revealed that the Hobo Spider was the actual cause of such bites in the northwest, and the spiders' ability to produce necrotic lesions and systemic illness was demonstrated in the laboratory in 1986.

The reason hobo spiders have a reputation for being so aggressive is because they have very poor eye sight and have to aggressively attack their prey to catch it. Their web is not sticky either which makes it harder for them to catch prey. Therefore with their poor eye sight, they think humans or anything that moves probably, are prey and attack. In around 50% of bites, no venom is injected, However when it is injected, necrosis occurs and the resulting wound can take years to heal with much skin being eaten away!

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