The Black Widow
So beautiful, so filled with wonder
You have class with the Arachnids
Latrodectus mactans is your scientific name
Your venomous bite is what gives your fame
Beware of her sting, she'll get you on the arm
Fall not for her false lustrous black charm
Avoid her at all costs, don't get too close
Her neurotoxin will take your breath away
For then they may be doing your post.
Louis B. Caruana, PhD., Copyright 1997-2009, all rights reserved worldwide.
The Widow Spiders
The widow spiders belong to the genus Latrodectus . There are five species found in North America north of Mexico. The black widow for many years was considered to be a single species but since is now recognized to be represented by three species, which are very similar in appearance and habitat. These three widow spiders are the Southern black widow Latrodectus mactans (Fabricius), the Western black widow L. hesperus (Chamberlin & Ivie), and the Northern widow L. variolus (Walckenaer). The widow spiders are the most notorious of all spiders. L. geometricus (C.L. Koch), the brown widow is found in California and southern Florida and throughout Africa. The red-legged widow, L. bishopi (Kaston) is limited to southern Florida. The venom, a neurotoxin, is highly virulent in all the widow spiders. Some report that the widow spiders are aggressive but observations shows that they are very timid and have no instinct to bite humans. When disturbed in their web, the widow spider attempts to escape rather than attack. Most deaths in the United States attributed spider bites are caused by the widow spiders, rarely is the brown recluse's bite lethal. The black widow spider is nocturnal. The best time to observe their presence in an area is a night.
Natural Enemies
The widow spiders have few natural enemies as is true for most species of spiders. Predators of the adult spiders include a few species of wasps, most notably the blue mud dauber and the spider wasp and, perhaps, the fire ants. Other species of spiders may pray on the widows, especially on the Redback spiders.
The Southern black widow spider - Latrodectus mactans is distributed from southern New England to Florida west to eastern Oklahoma, Texas and Kansas. They are more common in the southern part of their geographical range, hence their name "southern black widow". The jet black color, rounded abdomen, and red hourglass marking on abdomen is distinctive for for this spider. Adult spiders average 1.5 inches long. The female black widow spider is the one usually seen, as the male is often eaten by the female after mating. This does not mean that male spiders do not exist, they do. The widow spiders characteristically spins tangled webs, which look similar to spun cotton candy. Their webs are usually built in or beneath objects close to the ground such as under porches, under foundations of buildings, the lose bark of trees, and in basements. The bite of the black widow is painful and may cause death if medical attention is not sought immediately. The venom of this spider is highly neurotoxic and respiratory failure can occur if appropriate medications are not administered at once. Fortunately, the black widow is shy and does not bite without great provocation. The spider normally resides in an coarse, irregular web. The adult female spider will bit if she feels her young are threated. If bitten by a black widow place ice wrapped in a washcloth or other suitable covering on the site of the bite for 10 minutes and then off for 10 minutes. Repeat this process. Before applying ice at the site of the bit, it should be wiped with alcohol or household ammonia to relieve local swelling and prevent secondary bacterial infection. However, it is essential to seek immediate emergency medical treatment. Do not attempt to apply home first aid as a sole treatment.
Click on to the various websites listed below to get more information on all of these spiders.
Geographical Distribution
Southern black widow Latrodectus mactans (Fabricius)is found in southern New England states to Florida west to eastern Oklahoma, Texas and Kansas being more common in the southern range.
Spider Venom
All spiders, with the exception of two very small families, have poison glands. The spider�s venom is used to kill their prey. All spiders are exclusively carnivorous and generally prey only on live small animals. Spiders chiefly dine on insects. Preying on mosquitoes, for example, makes the spider beneficial in the control of mosquito-borne disease such as encephalitis. Some spider species are used to help control insects from destroying grain crops such as wheat. Spiders use their venom as a means to gain food and for defense. The vast majority of spiders do not produce venom virulent enough to harm humans. Too, spiders are timid creatures and bite and inject venom only in self-defense. Most spiders will run away as fast as they can, however, if felt cornered or in the protection of their young, they will bit humans.
Arachnidism
Arachnidism is a medical term used to describe the symptoms and pathology produced by the venom of the poisonous spiders, i.e. the black widows and the brown recluse (violin spider). It may be either a systemic reaction or a necrotic local lesion. The black widow spider (Latrodectus mactans) characteristically produces a systemic reaction because its venom is a neurotoxin. In contrast, the brown recluse spider (Loxosceles recluse) venom produces a necrotic local lesion at the site of the bite but can cause systemic reaction such as DIC. Necrotic arachnidism is mainly reported in cases having been due to envenomation by Loxosceles recluse, there have been some cases caused by the bit of L. unicolor , L. rufescens and L. arizonica. Not all Loxosceles species. All black widow and most brown widow spiders are poisonous for humans. Emergency medical first aid is indicated with the bite of any of these spider bites, especially the black widow because of its neurotoxic envenomation.
Envenomation Symptoms
Black Widow spiders - - painful rigidity of the abdominal wall muscles, tremors, nausea, vomiting, leg cramps, �tightness�� of chest, and rise of blood pressure. Severe cases are hallmarked by difficulty in breathing and unconsciousness, which may lead to death due to asphyxia preceded by convulsions. Fewer than 5 percent of people bitten by the black widow die.
Recluse spiders - - local reaction to envenom nation includes erythema, tenderness and bleb formation at the site of the bite, and later, ulceration appears which is very slow to heal. Typically the tissue dies and sloughs away leaving eschar. Complications include kidney damage associated with intravascular hemolysis. Prompt administration of corticosteroids is indicated. Systemic reactions include a stinging sensation followed by intense pain, fever, chills, nausea, weakness, restlessness or joint pain. These symptoms overlap with those of other medical conditions, please consult professional advice before making a conclusion unless you are sure of the identity of the recluse spider.
First-aid
Apply ice pack, house hold ammonia or alcohol directly to the bite area to relieve local swelling and pain. Apply tincture of iodine or other antiseptic to the site of the bite to prevent infection. Bed rest is indicated. If symptoms appear sever or in the neurotic envenomation of young children, the patient should be taken to a physician at once. Bring along the spider for identification, if possible, should antivenin be available. Antivenin is available to treat some widow spider bites.
Emergency Medical Advice eMedicine.com's Widow Spider Envenomation .
Black Widow Spider Bites Clinical Resources
Non-Traumatic Emergencies - Spider Bites : Informations Sheet from Loyola University Health System, Loyola University Chicago.
A Word About Bites And Stings - From the Hobo Spider Web Site.
Control and Prevention Information - Click here and scroll down to the heading "Control...". Remember, the black widow spider is nocturnal. If you want to be sure you have eliminated a black widow infestation, it is best to search for their presence at night with a flashlight.
For additional information and articles on the venomous spiders, go to Peter Hansen's (Denmark) website http://venomous-spiders.nanders.dk/.
General Description: The brown recluse spiders (genus: Loxosceles) are members of the family LOXOSCELIDAE, a small family that construct small irregular webs under logs, stones, and other secluded places, but they also are found indoors where they hide in dark corners, in storage trunks, in closets, bathrooms, cluttered cellars, corners and crevices.
General Range & Scientific Names: The general range of the brown recluse spider is dependent upon the species. However, the brown recluse maybe found in the south from California to Virginia and as far north as Nebraska, Iowa, Illinois, Indiana, and Ohio. Five species live in Texas, which are Loxosceles apachae, L. blanda, L. devia, and two that are considered venomous to humans, L. reculsa and L. rufescens.
Behavior: The brown recluse spiders exclusively hunt at night. Humans are bitten while asleep, when rolling onto a spider. Most commonly people are bitten while putting on clothing and sometimes in the bathroom or other habitats of the recluse spiders.
Brown recluse spider bites are difficult to diagnose. When possible, the spider should be saved for identification by a qualified healthcare practitioner or entomologist. The bite is usually painless at the time of occurrence, becoming reddened several hours later. In some cases, painful ulcers and scarring can develop in the days following.
Symptoms: Include stinging sensation followed by intense pain, fever, chills, nausea, weakness, and joint pain. All of the clinical symptoms might not be present. The physical reaction to a brown recluse spider bite depends on the amount of venom injected and an individual's sensitivity to it. Most people bitten by a brown recluse reported the bite being painless. There has been several reports in the medical literature of severe intravascular hemolysis associated with brown recluse spider envenomation. Often the skin lesion at the spider bite demonstrates a slow to heal necrotic ulcer caused by the spiders venom.
First-Aid: Apply an ice pack directly to the bite area to relieve swelling and pain. Collect the spider (even a mangled specimen has diagnostic value), if possible, for positive identification by a spider expert. A plastic bag, small jar, or pill vial is useful and no preservative is necessary, but rubbing alcohol helps to preserve the spider.
Internet Resources On The Brown Recluse Spiders
Hobo Spiders ( Tegenaria agrestis ) are brown in color and the female measures 12 to 18 mm in length. The male is slightly smaller. Their legs are long and show no distinct rings. Their abdomens have several chevron shaped markings. Males are distinctively different from females in that they have two large palps that look like boxing gloves. The females also have these palps, but the ends are not swollen as they are on the males. Females tend to have a larger and rounder abdomen when compared to males. Males and females may live peacefully together in the same web for two or three months during the mating season. Mature specimens may be found in all seasons and are known to live for several years. The hobo is one of the funnel-weaving spiders. They may be found in and around the house. They may be found in cellars, dark corners of rooms and other habitats that one might find funnel-weaving spiders. Although the hobo spider has a greater tendency to bite and is more aggressive than most, it does not seek out humans. When it does bite humans, it is because in might get into bedding or clothing and is trapped next to the exposed skin. Systematic reactions to the hobo spider poisoning include severe headaches, nausea, vomiting, soreness and flu-like symptoms. A ulcerative lesion is typical at the site of the spider bite. Seek medical attention promptly, if you think you have been bitten by the hobo spider.
Information On The Other Spiders
Entomology is the branch of zoology dealing with the scientific study of insects, including their taxonomy, morphology, physiology, and ecology. Applied aspects of entomology, such as the harmful and beneficial impact of insects on humans, are also studied.
Araneology is the branch of zoology that deals with the study of spiders.
Common Spiders Found In and Around Buildings and Homes
Most spiders found in and around homes are usually harmless. They will not harm you if you don't bother them. Never the less, one should be certain a venomous spider hasn't been sighted.
Venomous spiders have been discussed above. Illustrations and resources on the spiders of medical importance, the venomous spiders, are provided on this and other websites. The following sites might be of assistance in identifying that spider you found in its web in or near your home.
Spiders in The News
The widow spider along with the brown or fiddle-back spider - Loxosceles reclusa - are the two most poisonous spiders found in the United States. The brown reculse spider's bite is necrotizing and the site of the bite is very slow to heal. A complication of the brown spider's bite is DIC. Again, the black widow spider can be recognized by the red hourglass marking on its ventral side of the abdomen. The brown recluse spider is somewhat smaller (the body of the spider and its legs cover the size of a quarter) than the black widow and has a characteristic fiddle or violin marking on
its back (dorsal side near the top of the spider). The brown widow spiders are easily differentiated from the brown recluse because the brown widowed spiders have a similar appearance to that of the black widows and, of course, lack the fiddle marking. The brown recluse spiders are very timid, hence the scientific species name - reclusa. Their habitat includes garages, wood piles, bathrooms, closets, cellars, corners and crevices, drain pipes, under logs and rocks. These locations suggest the widow spiders like a place out of the way, so to speak. Since they may be found in closets and in old stored clothes, remember to check your cloths before you put them on. A brown recluse spider may be hiding in them and all you have to do is shake them out. This practice might prevent a dangerous spider bite. There has been reports of heavy infestation of brown recluse spiders in dwellings without an incidence of human bites.
Happy spider surfing! And remember spiders are beneficial in the control of insects, don't indiscriminately kill them.
Western black widow L. hesperus (Chamberlin & Ivie)is found in Western Texas, Oklahoma and Kansas north to the adjacent Canadian provinces and west to the Pacific Coast States.
The "brown widow" L. geometricus (C.L. Koch) is found in California and southern Florida and throughout Africa.
The Northern widow L. variolus (Walckenaer) is found in New England and adjacent Canada south to Florida, and west to eastern Texas, Oklahoma and Kansas, being more common in the northern part of the range.
For additional advice go to Widow Spider Envenomation : Medical information from eMedicine (Emergency Medicine topic).
Clinical Resources by Topic: Emergency Medicine
Black Widow Spider Bites
Online resources compiled by The University of Alabama Health Sciences Library.
Internet Resources On The Black Widow Spiders
The Department of Entomology at Texas A&M University, College Station, TX is an excellent resource for those interested in entomology.
Recommended websites - Professor John A. Jackman's Spiders and web page on the southern black widow . The southern black widow image on this page can be enlarged.
Internet Resources On The Brown Widow Spiders
Brown Recluse Spiders
The brown recluse spiders are often referred to as fiddleback or violin spiders because of their characteristic violin-shaped marking on the carapace of the cephalothorax (head-thorax region), which is useful in their identification. The violin pattern is common in adult brown recluse spiders; however, young spiders do not have any contrasting pigmentation. The general color is yellowish brown. The body and legs together cover an area about the size of a quarter but maybe a little larger.
An effective commercial antivenin is not available. In the past surgical removal of tissue was the standard procedure, but now this is thought to slow down wound healing. Some physicians administer high doses of cortisone-type hormones to combat hemolysis and other systemic complications.
Internet Resources and Description of the Hobo Spider
Geographical Distribution
The hobo spiders originated from Europe. They are believed to have been transported to the United States by shipping lanes and ended up in Seattle, Washington in the early 1980s. Since then they have slowly expanded throughout the Northwestern United States and Western Canada. The hobo spider has not known to live in California. Despite their increasing range and population, public awareness of these spiders has been surprisingly low, primarily because the brown recluse spider has been inaccurately blamed for the bites that people receive from Hobo Spiders.
General Educational Material on Spiders and Their Relatives
General Educational Material on General Biology and the Related Sciences
Educational Opportunities: Graduate Studies and Fellowships
Collecting Spiders
Spider Conservation
Entomology Websites
Professional Associations and Organizations
Misc. Sites on Spiders
Louis B. Caruana, Ph.D., MT(ASCP)
Distinguished Professor Emeritus,
College of Health Professions,
Texas State University-San Marcos,
San Marcos, Texas 78666
( Official Texas State Disclaimer )
loucaruana@txstate.edu
Louis B. Caruana, Ph.D., Copyright 2001- 2009, all rights reserved worldwide. Website Administrator.
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