Identification

More than several thousand species of spiders exist in the U.S. Two of the most common venomous and more common household spiders found in the Pacific Northwest include the Black Widow and Hobo Spider. While all spiders produce venom that is poisonous to their normal prey, these spiders have a lethal injection that can cause serious side effects to humans. Please seek medical help immediately for bites stemming from either of these species.

Female Black Widows are one and a half inches in diameter and jet black with red or yellow markings on the underside of the abdomen that resemble an hourglass. The much smaller males are light-colored with white or yellow stripes on their abdomens. In general, Black Widows are not particularly aggressive and rarely cause bite injuries unless disturbed. However, since the venom is toxic to the nervous system, a small bite may lead to systemic effects including convulsions and even death. Most bites occur when reaching under furniture or lifting objects where a spider is hiding.

Hobo Spiders are nearly two inches in diameter with long, hairy legs and chevron-shaped abdominal markings. They also move very fast. Females generally have larger abdomens than males. Reported bites from this spider are relatively rare, despite its aggressive nature. However, when bites do occur, the venom is necrotic, causing open, localized wounds that are slow to heal.

Brown Recluse Spiders are one inch in diameter and yellow to dark brown. They have a distinctive violin-shaped mark that runs down the top of the head and thorax. They are not particularly aggressive and usually retreat to cover when disturbed. Most bites occur when a person traps or crushes the spider by rolling on the spider while asleep in bed. Within 8-12 hours, the pain increases in intensity and after a few days, a large sore appears which heals very slowly and often leaves a scar.

Other species that do not pose as much of a threat to humans but are also common include the Funnel Weaver, House or Cobweb Spider, Ground or Wolf Spider, Jumping Spider, Crab Spider, Sac Spider, Orb Weaver or Garden Spider, Cat-faced Spider, Cellar or Daddy Long-Leg Spider, Harvestman Spider, and Fishing or Nursery-Web Spider.

Education

Most spiders are seldom seen, except from late August to early October when they are more active. They usually live in neglected areas, including:

  • Attics
  • Crawlspaces
  • Basements
  • Behind and under furniture, bookcases, or appliances
  • In corners and cracks between boards

They produce silk, secreted as liquid that hardens with the air. Different types and textures of silk may be used to construct snares and webs to capture prey as well as egg sacs, draglines, and ballooning threads. Draglines and ballooning threads are used by spiders to move/swing from one location to another. After climbing to a high point, some spiderlings will release ballooning threads to disperse themselves to new areas. The young are then seen sailing through the air on wind currents that have caught the ballooning threads. Depending upon the species, spiders lay eggs within a silk egg sac that is often ball-shaped and either hidden in the web or carried by the female. They may produce several egg sacs, each containing several hundred eggs, or as many as 3,000 eggs in a series of several sacs over a period of time. Eggs may hatch a few weeks later or not until the following spring. After molting four to 12 times, all spiders reach adulthood in about a year. Most spiders live either one to two seasons and some may die as soon as they mate or produce egg sacs.

In the Pacific Northwest, Black Widow Spiders primarily thrive in dry, undisturbed areas including firewood piles, old lumber, crawlspaces, bales of hay, and other similar areas. When found in homes, they are usually under appliances or heavy furniture. Female Black Widows spin silken webs usually in protected places under stones, house steps, decks, ground trash, or an overhanging embankment. The webs are irregularly shaped with strands running in many directions. They also hide during the day and hang upside-down in their webs at night. From May to October, Female Black Widows will lay and guard their egg sacs until the young are ready to hatch. During their one- to two-year life span, the females will produce several egg sacs, each containing several hundred eggs.

Hobo Spiders are typically found in and around houses, barns, and sheds. These spiders create webs similar to those of funnel weaver spiders, residing at the narrow end of their webs, ready to pounce on their prey. These include flies, cockroaches, crickets, earwigs, silverfish, pill bugs, various beetles, and other spiders. Also, the web is not sticky like that produced by other spiders, but traps insects that are unable to navigate on the surface. The lifecycle of Hobo Spiders is seasonal, with eggs hatching in April or May. As males mature, they leave their webs in search of females for mating, and then die. Females will lay their egg sacs and also die. Eggs don’t hatch until the following spring.

Brown Recluse Spiders are usually found indoors in bathrooms, bedrooms, closets, garages, basements, and cellars. They also prefer to reside in and around ductwork or registers and attics. Their webs are off-white to gray and found in secluded locations such as seldom-used shoes and clothes. Females will lay from one to five egg sacs, each containing 40-50 eggs, during her lifetime. Spiderlings emerge in about 30 days.

Funnel Weaver Spiders are primarily seen in late summer when morning dew makes their webs in lawns more visible. They are about half an inch long and have various marking in shades of gray, brown, white, black, and dull yellow. Like the Hobo Spider, these spiders are members of the funnel-web group. They hide at the narrow end of their funnels and wait until they feel the vibration of an insect crossing the web. When this happens, they dash out, bite the insect, and carry it back to the narrow end of the funnel. Females deposit their disc-shaped egg sacs in crevices, then die. They are sometimes found still clinging to the egg sacs even after death.

Female House or Cobweb Spiders are one-third of an inch long and larger than the males. They are gray to brown and have a mottled, globular abdomen that has several dark stripes on the upper side. They prefer to spin their webs in dark corners of moist rooms and hang upside down in the center of an irregular cobweb. The sticky threads entangle many insects, which are then bitten and depleted of blood. Webs become dust-covered when abandoned. Fertilized several times during her lifetime, the female will produce up to nine egg sacs, each containing 200 or more eggs. Hatching occurs in about eight days, but the young will stay within the sac until after the first molt. They are also cannibalistic, eating one another, and may take several months to mature.

Ground or Wolf Spiders are large, about half an inch long, and hairy. Their bodies are covered with shades of brown, black, gray, white, yellow, orange, or green. Many have a stripe or pattern the length of the first body segment and sometimes on the second. They run rapidly after prey and as such are often confused with tarantulas. They are nocturnal and may wander indoors in late summer and fall when temperatures cool. They are usually found in cellars and basements. These hunting spiders do not construct webs; rather, the large, globular egg sac is attached to spinnerets under the abdomen of the female. Upon hatching, the spiderlings will climb onto their mother’s back and stay there several days before dispersing. They will not establish themselves indoors and are not aggressive, but may bite if handled or molested.

Jumping Spiders are about half an inch long or less, stocky, and have short legs. The legs enable them to jump several times their own length. Their movements are quick with short, sudden jumps. They are also hairy with bright colors that resemble iridescent scales. Some are black with spots of orange or red on the top surface of the abdomen. Others are brownish-gray and yellow with white markings. Two of their eight eyes are very large on the face and their eye color can be changed as needed. They depend on their vision and leaping ability to catch prey, especially flies. Some may bite humans. They are active during the day and like sunshine. After mating, the female constructs a silk cocoon for her eggs and guards it.

Crab Spiders walk forward, backward and sideways like a crab, hence the name. Their bodies are compressed from top to bottom, giving a stocky appearance, and the first two pairs of legs are larger than the last two pairs. They are about an inch long or less. Also, males are smaller than females and have much longer legs. Many have “horns” or ornaments on the head or abdomen. Some Crab Spiders mimic the colors of the flowers upon which they rest to ambush their prey. As such, they come in bright colors of red, yellow, orange, white, and/or green. Others will inhabit trees or hunt along the ground and come in shades of gray, brown, or black. They do not make webs, but females lay their eggs in a sac and die before the eggs hatch.

Sac Spiders are sometimes called Two-Clawed Hunting Spiders because they have two claws at the tip of their legs. They are suspected of being responsible for most indoor bites, but no deaths have been reported. Since their venom is cytotoxic, only the tissues around the bite site are affected. These hunting spiders do not build webs, but construct flat, tubular sacs that can open at both ends. The sacs are found in rolled leaves, crevices, or under loose bark. These light-green to yellow-white spiders have a dark strip on the front portion of the upper-midline of the abdomen which is flat. Females are about three-quarters of an inch long, whereas males are a quarter of an inch long. Their eight eyes are similar in size and neatly arranged in two rows across the front of the face. The jaws are brown, and the front legs are longer than the rear. Females place their white, paper-like egg sacs under a stone, in wall voids, or the upper corners of rooms. Sac Spiders roam ceilings and walls to seek prey. The indoor population will increase as the weather cools and food sources decline in the autumn.

The traditional circular, flat, wheel-like webs in which flying insects are trapped are constructed by Orb Weaver or Garden Spiders. These large, elaborate, and beautiful webs are found in gardens and tall vegetation, especially in late summer and early autumn. Since these spiders have poor vision, the prey is primarily detected by feeling the vibration of and tension of the threads in the web. They will then bite their victim and quickly wrap it with silk while spinning with their legs. The prey is then carried to the center of the web or to the corner where it is eaten. Inedible items are cut from the web and dropped to the ground. Female Orb Weavers produce egg sacs containing several hundred eggs, then die. Eggs may hatch soon after or not until the following spring. Many adults are large, and some have odd-shaped abdomens such as pointed spurs and conical tubercles that come in a variety of colors including black, yellow, orange, red, white, brown, and green.

A common Garden Spider is known as the Black-and-Yellow Garden Spider. It has silver hairs on the back of its front body section and a large abdomen marked in black and bright yellow or orange. The front legs are sometimes black or have a short band of orange. This spider is about one inch long and hangs upside down in the center of the web. Despite its formidable appearance, they are not considered dangerous, but can bite if handled or mistreated.

One of the most common but unusual spiders encountered is the Cat-Faced Spider. Full-grown females can be quite large, and have a combination of odd projections on the abdomen as well as dark indentation markings that resemble the ears and eyes of a cat, hence the name. Despite their large size and bizarre appearance, they are harmless to humans. Also, they tend to create webs near lights and in corners along the outside of buildings.

Cellar or Daddy Long-Leg Spiders have slender legs that can grow up to two inches long. Their whitish-yellow to pale gray bodies are about a third of an inch in length. Eyes are close together. They are commonly found in barns, cellars, and damp warehouses. Many hang upside-down in a loose web in dark corners of homes or cellars. Males and females live together, and when alarmed will shake the web violently. The female carries the round egg sac in her jaws.

Harvestmen are not considered spiders, yet resemble Cellar or Daddy Long Leg Spiders. They are tan to brown and have an oval-shaped, compact body and extremely long, slender legs. They may be found in gardens and outdoor buildings. Occasionally, they are found in homes, feeding on plant juices, dead insects, and some live insects.

Fishing or Nursery-Web Spiders resemble wolf spiders, due to their large size and three-inch leg span. They have excellent vision and may sit quietly for hours with their legs spread out on vegetation or boat docks, or hunt actively in vegetation. They feed on aquatic insects and sometimes small fish. Most can run across the surface of water and if chased, will dive and stay submerged for some time. Many live near lakes and streams, but occasionally are found indoors in moist areas. Females carry huge egg sacs in their jaws, which are located under their bodies. When hatching time is near, they will tie leaves together with silk around the eggs sacs and stand guard. Young spiders will leave the nursery about one week later.

Customer Preparation

Inside:

  • Use a strong suction vacuum cleaner with proper attachments to collect and destroy webs, egg sacs, and spiders.
  • Use a dust mop, stiff broom, and dustpan as needed to discourage any new spiders.
  • Move and dust behind and under furniture, stored materials, wall hangings, and corners of ceilings as often as possible.
  • Eliminate other household pests such as flies, ants, and cockroaches as they attract spiders.
  • Seal or caulk cracks and crevices around windows and doors.
  • Install tight-fitting screens as needed to prevent spiders from entering the house from outside.

Outside:

  • Control excess moisture and humidity by keeping basements, crawlspaces, and porches as dry as possible.
  • Clean up outdoor woodpiles, trash, rocks, compost piles, old boards, and other debris, especially around the foundation.
  • Use a hose with high-pressure water to knock down and destroy webs, egg sacs, and spiders on the outside of the home.
  • Use yellow or sodium vapor light bulbs around the outside entrances to reduce night-flying insects, which attract spiders.

Customer Expectations

Spiders will act abnormally prior to death. Either more or less will appear, climbing up walls to flee from treatment. Some may even appear from crawlspaces to die. Expect additional activity within the next 30 days as spiders continue to track through the residue. Our products will not only kill spiders on contact, but act as a repellent by leaving a long-term residue that outlasts their lifecycles.