Poisonous Spiders to Avoid – Black Widow and Brown Recluse

The call came out one hot, dry August afternoon. I had never seen my mother, so worried. We drove the short trip to the small hospital in our hometown, in no time. My father was in a bed upstairs, an IV dripping into one arm and a square bandage on the other. He was smiling, telling everyone not to worry that day.

But a day later, his arm had swollen, and the all-too-familiar lines of blood poisoning raced up and down in angry red stripes. It was touch and go for the better part of a week, but he pulled through. I’ll never forget the doctor inviting my mother and me into his office to show us a fat, round black spider in a small bottle of alcohol. It had a bright red drop of color on its belly.

Poisonous spiders cold facts

That was the start of my lifelong fascination with such creatures.

How could such a small, almost insignificant animal lay low a strapping 6′ 1″ 195-pound man in the prime of life?

A little animal designed to catch flies?

To avoid finding yourself in a predicament like my father’s, it’s best to know a little about the creatures and their habits. Understanding how they live and where they are apt to be found can help prevent any nasty encounters.

To begin with, all spiders are poisonous. There are no exceptions to this rule. The spider gets its food by piercing its prey with fangs and injecting venom to kill it. The fangs and the thick short stalks connecting them to the body are called chelicerae. Along with the venom, the spider also injects strong enzymes, which, in effect, liquefy the prey. The spider then literally drinks its supper, for the chelicerae, whether of the pinching, tong-like type, or the stabbing, recurved type are not suited to chew.

Black Widow On Tree Branch

Although all spiders kill their prey and ingest it in the same way, they have developed three main styles of prey gathering.

They hunt, running over the ground like the swift Wolf Spiders, ponderous Thrantulas and leaping Jumping Spiders.

They lay in ambush like the stocky Trap-door Spider, the chameleon-like Crab Spider that can change color to match its flower or the elegant Lynx Spider.

Or they entrap their prey in intricately woven webs. Of course, there are exceptions —such as the Spitting Spider, which actually shoots a jet of sticky gossamer to snag unwary passers-by; or the Fisher Spider, who is large and swims well enough to prey on minnows; and the Ant Spider, who mimics ants so successfully it can walk among armies of its prey undetected. By and large, however, spiders earn their living by hunting, ambushing, or trapping.

We are, perhaps, most familiar with web entrapment and the beautiful intricacy of the spider’s web. The web itself is manufactured entirely by the spider from ingredients produced internally and then spun in fine strands through its spinnerets.

Spider silk and web patterns

Despite the web’s apparent fragility, the silk from a spider’s web is strong. During the early days of WWII, this silk was used for crosshairs in bombsights. To spin this strong, delicate silk, the spider must draw from his inner resources. Research has proven that a spider can spin no more than three webs without eating, and, of course, without a web, he cannot trap prey to eat.


There are two types of webs, essentially, spun by spiders. Orb-Weavers produce the ornate, symmetrical webs known for their round, globular patterns. Although Orb-Weavers are among the largest spiders, there are none that we know to be seriously venomous. Among the Irregular-Web-Weavers, however, we find two of our most notorious villains, the Black Widow and the Brown Recluse.

The irregular web spun by these spiders tends to be of a sketchier design than the symmetrical orb. Essentially its design requires two long, strong planes for anchoring the ends of the web. Such planes are a prominent feature of the corners we designed into our own buildings.

Despite their reputations, these spiders generally demonstrate a shy, retiring nature. As an expression of this shyness, they choose to put their webs in hidden, out-of-the-way places. While spiders will certainly bite in self-defense, a good many mistakes undoubtedly occur when a stray hand or finger blunders into a web, and a hungry spider rushes out for a meal.

The Black Widow, Latrodectus mactans, likes to put its web in out of the way places such as hollow trees and deserted buildings. On one hunting trip, while standing on the back steps of a derelict farmhouse, I counted 12 Black Widows in the mudroom. Woodpiles, basements, and attics are other favored spots for web-spinning. Another preferred haunt that has provided some excruciating encounters is the out-house. The black widow has a fondness for nesting under the seat.

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The Most Poisonous Spiders

Although the Black Widow acquired its common name from the female’s tendency to eat the male after mating (a trait common to many spiders) rather than from the potency of its poison, it is the most seriously poisonous spider in the United States and perhaps the world.

Estimates place the strength of its venom at 15 times the strength of the Timber Rattlesnake’s, Black Widow venom has seven protein and three non-protein fractions. Of these, Protein Fraction B is the dangerous one for mammals, having 20 times the fatality potential of the whole venom. In this species, males and females are equally dangerous.

And the danger may be enhanced if you don’t realize that you’ve been bitten. Their recurved, stabbing fangs are relatively small. A bite has a sharp initial pain that feels like a needle puncture. There may be a burning sensation. If you’re distracted, perhaps because of heavy physical exertion, you may feel nothing. If you do look down to seek the source of the burning, you may see some redness and slight swelling.

More serious symptoms can begin 15 minutes to hours after the bite. Some of the first signs are a general weakness with a mild paralysis of the muscles in the region of the bite. This can be followed by the onset of abdominal muscular rigidity and cramping in your arms and legs. Your skin may feel cool and clammy even as you sweat. Your breathing may become labored, and your speech could be affected. Nausea could lead to vomiting. At its worst, stupor or delirium may occur. Small children may suffer convulsions. General weakness, nervousness, and muscle spasms may persist for months after the bite.

The confirmed mortality rate is just over 4 percent. Not high unless you are among that 4 percent.

Spider Bite
Spider Bite

Fortunately, first aid is relatively simple. Apply a cold compress, preferably an icebag, to the bite and take the victim to a doctor as quickly as possible. Remember in transit to keep the victim calm, avoiding any exertion, and do not elevate the bitten area. It is important to avoid any activity that will increase the heart rate for the increased heart rate will speed the spread of the poison through the system.

Also beware of any signs of shock and treat the victim for shock as needed. The Black Widow is not the only species of Latrodectus to worry about in America. Latrodectus hesperus, the Western Black Widow, is virtually identical to L. mactans in all ways, including the potency of the venom.

You may also run across the Brown Widow, L. geometricus, a gray spider with brown mottling but the same general configuration as L. mactans. Its venom is less virulent, but it can still be unpleasant. The same is true of L. bishopi, the Red-Legged Widow. In the far Southwest L. texanus lurks, a species which carries the bright markings of his immature state into adulthood. His too is a milder venom that can still cause considerable discomfort.

In short, stay away from all spiders with irregular webs and Latrodectus’ characteristic high-humped, round, fat abdomen and long legs. Another tip-off is the hourglass marking on the underside of the abdomen. This may be red, yellow, or both. Or, as in the Australian L. hasseltii, it may carry the mark on its back.

The Black Widow in all its variations has been known and feared worldwide. The Northern Mewuk Indians of California used to say, “Po’ko-moo, the small black spider with a red spot on his belly is poison. Sometimes he scratches people with his long fingers, and the scratch makes a bad sore” They suggested leaving Po’ko-moo alone. Not bad advice even today.

Brown Spiders

The other infamous weaver of irregular webs doesn’t have as many notches on his gun, but he may be far more dangerous. There are only seven deaths officially attributed to the Loxosceles genus, but they have not been recognized as a danger for as long as the Black Widow has. In the early 1960s, a rash of reports from careful observers, recorded the worst: the bite of Loxosceles could be fatal. It makes you wonder how many previous bites were written off to rusty nails or septic splinters.

Members of this genus are commonly known as Brown Spiders because of their coloring, which ranges from a yellowish shade to a deeper brown most pronounced on the legs and abdomen. These are medium-sized spiders, growing to a body length of about one-third of an inch. Like the Black Widow, they have small, recurving, stabbing fangs.

Another common name is the Fiddle back or Violin spider, which is derived from the characteristic marking that extends backward from the head down the cephalothorax. When the spider is facing you, it will look like a right-side-up violin. This marking is common to all spiders in the genus, but it is not always well defined or continuous.

The part that forms the body of the violin, an elevated portion of the head around the eyes called the ocular tubercle is not always colored dark enough to make this identifying feature stand out.

Unfortunately, this genus does not have other significant outstanding features to aid in recognition. It does have extremely long legs, but so do many other spiders. One should exercise caution in identification.

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While the female Black Widow may be five times larger than her mate with a body length of 1 ¼ ” to his ¼ “, the males and females of the Loxosceles genus are virtually the same sizes, and the male Brown Spider will most likely not be eaten by his mate after the mating.

Although different experts embrace different opinions as to the potency of male versus female venom, I find it best to consider male and female specimens equally dangerous.

There are several varieties of Brown Spiders common to the United States. They thrive in human habitations, although they may also be found in the wild under rocks and fallen logs. They particularly enjoy basements, garages, attics, and closets. Their large, irregular webs may appear to be flattened to accommodate the space in the secretive niches they favor.

They have been known to crawl into trunks, boxes, and clothing, a habit that accounts for the introduction of at least one foreign species and the spread of native species outside their normal range. Moving vans and ships’ holds have trans-ported more than one to new ground.

These are long-lived spiders with lifespans of several years. They are also noted for the female’s generous nature. Not only does she refrain from eating the male after courtship, but she also will guard the eggs and the recently hatched young. Such habits promote more potentially dangerous situations and increase the opportunity for infestation.

As these spiders live in our buildings safe from natural enemies, their numbers will increase more rapidly than they would if the female did not protect the young and did raise them outdoors amid their natural enemies.

Brown Recluse

Home invader

The Brown Recluse, Loxosceles reclusa, is the best known of this genus. Although it was originally believed that he was confined to the Midwest and Mid-South, his range has probably expanded. L. unicolor frequents the Southwest from California to Texas and has been involved in several recorded instances with serious consequences.

Another, L. laeta, was introduced from South America. It is reputed to be even more highly venomous than the native species. A population was found in the Sierra Madre, a suburb of Los Angeles, and another in Boston. L. rufescens lives in Eastern Europe and is probably overdue for an appearance in the U.S.

The bite of the Brown Recluse is not painful, and the onset of symptoms may be delayed for as long as eight hours. The first symptoms may be discoloration at the site of the wound and blistering. If the bite has been particularly potent, you may feel general nausea and have a fever with a rash and severe abdominal cramps.

The wound itself, however, may not be particularly painful. Typically, it will range in size from a dime to a half-dollar. The skin in the area surrounding the wound will then decompose and fall out, leaving a depression something like a bullet wound. The wound will stay open, unhealed for months, and it may grow, spreading until the surgery is required before healing can begin. In 1968 an Alabama man was bitten on the leg. He died five weeks later with an open wound 10 inches in diameter. The guilty spider was the Brown Recluse.

These two genera of spiders represent the greatest threats to our safety and well-being, but they are not the only spiders who have killed men. Lycosa carolinensis, the largest American Wolf Spider, and Phidippus johnsoni, a furry little Jumping Spider, are responsible for two fatalities, one an elderly woman, the other an infant. Both deaths were caused not by the potency of the venom but by the victims’ allergic reactions to the bite.

Any venom is capable of causing such an allergic reaction. In the 1950s, 124 Americans died from bee stings; snakes killed 138. The onset of the symptoms of an allergic reaction can be swift, causing death within 16 to 30 minutes. People suffering from suspected hyperallergic reactions can often be desensitized. If this is not possible, it is best to know your condition and take the necessary precautions. If you have any doubts as to your status, discuss the matter with a specialist who can advise you on what precautions to take.

There is one other consideration in our discussion of spiders. The Tarantula is a large, hairy fellow familiar to all. Each year just prior to their September into October, mating season swarms of the brown males will be seen traveling across their territories in the Southwest. At this time, they are particularly prone to bite, even without provocation. While their venom is no more harmful than a bee sting, their fangs are capable of producing appreciable puncture wounds.

Many spiders besides Tarantulas have large fangs, and the puncture wound is one of the most susceptible to infection. Venom should not be considered a cleansing agent. If anything, knowing the habits of spiders, should prompt you to make a serious effort to obtain professional medical care for such puncture wounds. You never know where those fangs have been.

The best way to avoid a spider’s fangs is to stay away from spiders. Normally, they are easy to stay clear of, but when they infest your home, you must remove them. The best way to clean storage areas, attics, closets, and such of potentially harmful interlopers is to vacuum the area with an extension tube fitted with an attachment big enough to suck up a spider. Be careful when disposing of the bag or its contents, for any reviving spider is apt to be agitated by his experience. Pesticides are effective if you’re not worried about the contamination of their chemical residues.

Never handle a dead spider. The mechanics of a spider’s fang apparatus are such that it can deliver a bite from any angle without blocking the venom duct. Coupled with the fact that spider fangs are extremely sharp, the possibility of accidental envenomation is too great to justify the risk of handling an apparently dead spider.

If you think you might have a serious infestation, which may occur with relatives of the Brown Recluse, it would be wise to call a professional exterminator. No area is safe from the possibility of infiltration. Young spider-hags have a unique model of transportation that opens the world to them: They spin a strand of silk, offer it to the air and use its natural buoyancy to lift them into wind currents.

Ships hundreds of miles at sea and planes more than 10,000 feet in the air have encountered these ballooning baby spiders. Newborn spiders are very tiny. They have no trouble insinuating themselves through cracks and fissures, screens in many kinds of entryways, drains, and ventilation systems.


All spiders are poisonous, but take particular care when approaching any spider similar to Latrodectus or Loxosceles. It is common for minor variations in color and markings to occur in any species of spider. Small variations can seem like big differences in small animals. These poisonous spiders have earned the right to your respect.

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