Wolf Spiders Wolf spiders are fairly large hunting spiders that often cause alarm because of their appearance. Most are gray or brown and fast moving. Many species exist and most are about 1/2 inch in length. One genus of wolf spiders, the giant burrowing spider, may be 1-1/2 inches. Wolf spiders most commonly enter homes late in the season. They hide in cracks and do not produce webbing. Larger species can produce a mildly painful bite, but symptoms do not last long.
Jumping Spiders Jumping spiders are brightly colored active spiders. Their bodies are often densely covered with colored hairs and some may appear iridescent. They have a stout body and large eyes. They are active during the day and may jump or move sideways with ease. They rarely reproduce in homes and often appear as late season invaders after frost.
Orb Weavers Orb weavers produce characteristic large webs that have radiating threads from a central point. Some of the orb weavers become quite large, such as the common garden argiopes and the monkey faced or cat faced spiders. They attract attention because of their conspicuous size and web. They rarely enter homes.
Funnel Weavers Funnel weavers are medium sized spiders varying from 1/8 to 3/4 inch in length. Their funnel webs are easily seen on lawns in late summer. Funnel weavers may also inhabit corners of cellars or outbuildings. Egg sacs are often laid in a cocoon that remains attached to the web.
Cobweb Spiders Cobweb spiders are very common in homes and many are well adapted to survival indoors. These are small to medium sized spiders that typically are found hanging upside down from irregular webs in corners of rooms and other darkened areas. When prey is tangled in the web, they throw anchoring silk strands over it. They do not completely wrap the prey, as do the orb weavers. Although almost all cobweb weavers are harmless, the black widows also belong to this family of spiders.
Black Widow Spiders The black widow is a common species in many parts of Utah. Black widows produce a loose web and prefer to inhabit dark, undisturbed areas. Typical locations of black widow nests include locations such as shrubbery, around log piles, in crawl spaces, under porches, in garages, and around piled debris.
Essentially, all human bites occur from the female black widow, often as she is guarding her egg sac. A grown female is about 1/2 inch in length and appears shiny black or dark brown with a spherical abdomen. Most black widows also have orange-red markings on the underside of the abdomen, sometimes appearing as an hourglass. However these markings may be reduced and even absent among many of the black widows.
The venom of the black widow spider is a nerve poison that produces distinctive symptoms. Often the original bite is not painful. It then produces a burning sensation with local swelling and redness. Pain may become intense in one to three hours and last p to 48 hours. Cramping of the legs, arms and chest may follow. The abdominal muscles become rigid in many cases.
Black widow bites should receive prompt medical attention. Although fatalities are very rare, symptoms are very painful. Antiserums are available and injections of calcium gluconate can help to relieve symptoms. When possible, transport the spider and the victim to the doctor. This will allow proper identification and treatment. If a spider is crushed during capture it may not be recognizable.
The Hobo Spider The hobo spider, sometimes called the aggressive house spider, was first identified in Utah in 1990. The hobo spider is of importance because its bite causes necrotic wounds similar to those of the brown recluse spider. The hobo spider builds funnel or tube shaped webs. It is a long legged and swift running spider. It has a brown cephalothorax and brown legs. The abdomen has a distinctive pattern of yellowish markings on a grayish background, although this pattern ma hard to see without a microscope. The complete life cycle of the hobo spider lasts for two years. Hobo spiders prefer to use habitats that have holes or cracks to support the funnel like webs. They are poor climbers and are rarely seen above ground level. Hobo spiders are most commonly encountered from June through September when males wander in search of females. For this reason, most bites occur during July through September. Males generally have a more toxic bite than females, while immature hobo spider bites seem to produce the most serious wounds. females of the species tend to stay in their webs and are not usually found running about.
The hobo spider is medically important because of its ability to cause necrotic wounds. Necrotic spider bites have been reported in Utah for many years and are usually blamed on the brown recluse spider.
As of 2003, only a few specimens of the brown recluse spider have been documented in Utah and these were imported. The bite of the hobo spider is relatively painless and is reported to feel like a pinprick. Within fifteen minutes of the bite, numbing sensations may occur at the bite site and other areas of the body and dizziness may occur. After about one hour, reddening around the bite begins and enlarges in area. The bite site becomes hardened and swollen within about 18 hours. Blistering at the bite, visual or auditory disturbances, severe headache, weakness, and joint pains may occur within the first 36 hours. Within 24 to 36 hours, a discharge of fluids and blistering may occur. After 2 or 3 days, the area around the wound may blacken. After seven to ten days, the necrotic area will usually take on a characteristic elliptical shape. Spells of nausea and sweating often persist through this time period and headaches may persist even longer.
If a bite is suspected to be that of a hobo spider, seek immediate medical attention. The treatment for all necrotic spider bites is similar.
BIOLOGY AND BEHAVIOR Spiders are a group of animals classified as arachnids. They are not insects, instead being more closely related to mites and ticks. Spiders are characterized by having eight legs and the two distinct body regions of the cephalothorax and abdomen. All spiders feed only on insects and other small arthropods. Their activities are highly beneficial since they help control many pest species in yards and in and around homes.
Unfortunately, there is a widespread fear of spiders by people. 25 Spider fears also exist because of a few poisonous species such as the black widow. Many spider species occur throughout Utah. They begin life as eggs laid in egg sacs that are bound by silk. These eggs sacks may be guarded or even carried by the female. The young spiders, known as spiderlings, emerge from the eggs and scatter. Many spiders disperse by ballooning. This occurs by spiders producing silken threads that are caught by the wind. Although they do not have wings, spiderlings have been carried hundreds of miles on wind currents. The developing spiders feed and grow over a period of several months. Spiders molt several times before becoming fully grown.
Many common spiders have one generation per year and become full grown in late summer. However habits vary and mating and egg laying can occur during almost any time during the year depending on the species. All spiders can produce silk. Many of the more conspicuous species build webs to capture prey. Some spiders do not produce a web, but instead hunt their prey. These spiders ambush prey and use their silk for building egg sacs or retreats. Spiders eat live prey. Victims are killed by venom that the spider injects through fangs.
Spiders may survive for months without food. Most species of spiders found in homes are attracted to water sources. Water pipes, floor drains, and plumbing fixtures commonly attract spiders. Some spiders prefer warm, dry, undisturbed sites and can be found in air vents or room corners. Spiders found indoors often hide in cracks, darkened areas, or silken retreats they have built.
Movement of spiders into homes greatly accelerates after cool weather arrives in early fall. Also, male spiders of most species are often highly mobile and range widely while searching for mates.
Although all spiders bite and produce venom, few pose any health threat. The venom of most spiders is not very toxic to humans and many smaller spiders cannot break the skin. Also, spiders are not usually aggressive and only bite when accidentally handled or trapped. Two poisonous species of spiders do occur in Utah, the black widow and the hobo spider.
SPIDER CONTROL METHODS Control methods for spiders are most effective if they include habitat elimination, exclusion, avoidance of risk, and chemical control. Keep shelter materials such as rocks, debris, and trash away from the building foundations. Seal cracks and other openings. Apply insecticides to exterior foundations. In cases of interior infestation, insecticides should be selected and applied according to label directions. Sticky traps and glue boards can be used to detect spiders and provide some degree of control.