Spider Mites are tiny insects with two pairs of legs and wings. They have four eyes, which they use to see their prey. Their bodies are covered with hair called setae, but not all spiders have them. Some species only have hairs on the upper surface of their body or none at all. All spider mites look alike because they share many characteristics such as size, shape and coloration (see Figure 1).
Figure 1: A typical spider with its characteristic black and white markings.
The most common type of spider mite found in homes is the brown recluse spider (Latrodectus hasselti) . These small, dark colored spiders live throughout North America, Europe and Asia.
They usually prefer warm climates like those in the northern United States, Canada and southern Europe. Brown recluses are often mistaken for other types of spiders since they resemble them so closely. However, brown recluses are not true spiders. They belong to the order Araneidae , a group of arachnids known as “true” spiders because they lack any functional legs.
Brown recluses are very difficult to kill because they don’t spin webs and their bite causes no symptoms other than minor pain. Many people think that if they get bitten by one of these spiders then it must be dangerous, however, there is little evidence that proves this assumption.
The best way to prevent a brown recluse bite is to avoid the spider altogether.
There are three types of spiders that fall into the recluse group. These are the Loxosceles reclusa, Loxosceles laeta and Loxosceles intermedia.
The Loxosceles reclusa can be found in central and southern United States, while the Loxosceles intermedia lives in southwest Asia. The Loxosceles laeta is found in South America. The coloration of all three species is very similar.
The spider measures about 6mm long when it is fully grown. It has a light brown color and a darker, kidney bean shaped marking on its back end.
Although the bite from a brown recluse often leads to a large area of dead tissue, it doesn’t always develop.
Most people bitten by this spider experience only minor pain, swelling and itching at the site of the bite. Some people experience a burning sensation and develop blisters at the site of the bite a few hours after being bitten.
These symptoms disappear completely within a month. In very rare cases where a large amount of tissue dies due to the bite, skin may turn black and slough off. A small number of these cases result in an infection that may lead to death if not treated with antibiotics.
Black widows are a group of spiders that have dangerous venom. The most well known of these deadly spiders is the black widow.
Their venom contains a toxin that breaks down nerve tissue causing muscle spasms, breathing difficulties and sometimes death in severe cases. There are three types of black widow spiders found in the United States; the western, the northern and the southern.
Black widows can be recognized by the distinctive red hour glass marking on its abdomen.
The adult female black widow is between ½ an inch and 1 inch long. The male is about ½ the size of the female and is not usually black, but brown or even grey in color.
The female’s web is an irregular network of sticky webs designed to trap insects. It is often found in dark places such as wood piles, garages, sheds and under stones.
Black widow spiders are found throughout the United States. They live in dark, cool habitats, such as logs, woodpiles, rock piles and exterior areas.
They spin messy webs in secluded places where they wait for insects or other prey to become trapped.
Black widows prefer warm, damp areas with loose gravel or sand, which are good for tunneling. Places where they like to make their homes include railroad tracks, gardens and woodpiles.
The bite of a black widow spider is very dangerous to humans and especially children, the elderly and anyone with a weakened immune system. The female black widow is particularly dangerous as it is more likely to enter human dwellings in search of prey.
The bite of a black widow spider causes the area around the bite to swell, and a small red mark appears where the fangs penetrated the skin. Within half an hour, severe pain begins in the region of the bite.
As the venom spreads through the body, further symptoms appear and these may include: nausea, vomiting, abdominal cramps, restlessness and cold sweats. In severe cases respiratory failure and paralysis can occur. A bite from a large female black widow is fatal in 3% of cases.
In some cases of a milder reaction, the patient may only experience general symptoms such as headaches, sore muscles and a mild fever for a few days after the bite. There is no antivenom available for black widow bites so treatment involves relieving the symptoms with antacids and painkillers.
Brown Recluse Spiders
The brown recluse is a member of a group of spiders called the recluses. These spiders have a dark brown color and are rarely noticed because they hide during the day and hunt at night, preferring dark places such as wood piles, basements and closets.
The webs of these spiders are sticky but irregular, and they usually have a disorderly appearance. If the spider is disturbed it will often run away rather than defend itself.
The brown recluse is a small spider with distinct dark brown coloring and a darker stripe on its back. It has a dark area around its eyes and a light-colored stomach.
It is also known as the fiddleback or violin spider because of this marking.
This spider bites when trapped between skin and clothes, such as in a shoe, or when trapped in bedsheets. The bite may cause severe illness and even death in some rare cases, usually due to complications.
Most bites do not have symptoms and heal completely without treatment.
The brown recluse bite often results in an open sore called a necrotic lesion, sometimes several, which forms at the site of the bite. The skin around this open sore dies and eventually falls off, exposing tender flesh that could become infected.
Other symptoms may include: fever, chills, nausea, vomiting, muscle aches, reduced appetite and tiredness. Severe reactions with widespread skin damage, organ failure and blood problems can be fatal.
However, death from a brown recluse bite is rare, affecting less than 1% of those bitten.
These spider bites are often treated with antiseptics and antibiotics but most heal on their own. Painkillers may also be used to relieve the pain.
In severe cases, skin grafts may be necessary.
Treatment should be sought as soon as possible after the spider bite.
The brown recluse does not have markings like a rattlesnake’s triangle or a black widow’s red mark. Its bite may be mild and still require medical treatment, or it may be deadly.
There is no way of knowing how any individual is going to react to the bite so immediate medical attention should be sought if bitten by one of these spiders.
The brown recluse is a shy and retiring animal. It keeps to itself and wanders no further than necessary in search of food.
It would rather not bite anything larger than a pinhead if it can avoid it. Unfortunately, human flesh is rather nutritious, even if the victim’s skin begins to decay at the site of the bite.
Most victims are children or elderly. Children are especially vulnerable to severe bites because their skin is softer and their immune systems less able to fight off infections.
The Brown Recluse is a native of North America but it has been transported to many other parts of the world in shipping containers or by people returning from holiday with souvenirs in their bags. It has been introduced into Australia, the Bahamas, Britain and New Zealand, as well as other isolated islands such as Hawaii.
It was first identified scientifically in 1872 and named Loxosceles reclusa.
Several other species have been identified which look alike but can be distinguished by small differences in the markings or coloring. These include:
The Chilean Recluse (L. laeta), The Mediterranean Recluse (L.
rufescens), The Texas Brown Spider (L. varia) and the Desert Recluse (L. deserta).
These are all similar enough to be confused with the Brown Recluse but they generally have not been known to be medically significant. The Desert Recluse can also deliver a serious bite but it is not known to live in the United States.
The most dangerous spider in North America that is not related to the Brown Recluse is the Hobo Spider (Tegenaria agrestis). This is a large hunting spider with a pattern of black stripes on a brown body and is common across much of North America.
It has caused highly toxic wounds to humans, especially children, but it is not a true spider ‘recluse’. It does not spin webs and instead wanders in search of prey.
The bite of the Black Widow is just as serious, if not more so, but it is found only in the southern states of the USA. It spins a web but does not lurk in it and instead sits in a silken retreat near its web.
However, the female is highly aggressive in defending its territory and any intrusion into this territory will trigger an attack.
The Black Widow is smaller than the Brown Recluse, being around half an inch in length. It is almost spherical rather than the more common globe-shaped spider with a skinny leg attachment area.
The Black Widow’s color varies but it is usually jet black with a red marking in the shape of an hourglass on the abdomen. It has a glossy sheen and the legs are fairly short in proportion to the body which is atypical of spiders.
This gives it a rather compact appearance.
Like the Brown Recluse, it can act as a hunter or scavenger and it is particularly partial to eating other spiders, which is unique amongst spiders. It is not a dangerous hunter and does not actively seek out prey but instead waits in its web and pulls it tight around whatever happens to be caught in it.
The toxin in the Black Widow’s venom is a complex mixture of chemicals. The most important of these is a neurotoxin that affects the nervous system causing progressive paralysis.
The symptoms of being bitten by a brown recluse spider are usually quite serious and potentially life-threatening. The bite site becomes damaged as the flesh dies and turns black.
The surrounding area then becomes swollen and painful.
Fever and chills are common with nausea, vomiting and diarrhea. Other symptoms may also develop but these will depend upon the victim’s state of health in the first place.
The actual bite does not necessarily hurt. Most people do not even notice they have been bitten at the time but a mild stinging sensation is not unusual.
It is not actually possible to feel all the small bites when a spider is found in your clothing or in bed.
It can take up to fourteen days for the bite to become life-threatening so early treatment is vital.
Treatment and Prevention
The treatment for a brown recluse bite is an anti-venom but this is not available everywhere so initial treatment consists of antibiotics to fight infection and painkillers. The wound should be gently debrided to remove dead and dying flesh.
The brown recluse is a nocturnal hunter and generally only ventures out when it is dark so it is vital to check over clothing, shoes and bedding before use. Any spider found in these places should be removed and released away from the house.
It is also important to look into cardboard boxes, wooden piles and areas around the house that are dark so that the spider can hunt without danger of being spotted.
Simple precautions such as these can often prevent bites from occurring in the first place.
If you do get bitten then clean and dress the wound immediately. For milder bites, over-the-counter painkillers may be sufficient but seek medical attention if the bite site becomes infected, painful or swells significantly.
Proper cleaning and over-the-counter painkillers will probably be sufficient for most brown recluse bites but if you do feel unwell after a bite then it is best to seek medical attention immediately.
The cutter ant is a particularly aggressive variety of the common fire ant. Native to South America, they have spread to other parts of the world as a result of human activity and now number in their millions.
The average cutter ant is around 1 cm long and is brownish in color but this can vary depending on where they live. They are also territorial so will normally be found in large numbers close together.
The ants normal mode of hunting is to bite their prey with their strong jaws and then use chemicals given off from their abdomen to numb the pain of the bite so the prey does not notice they are being attacked and eaten.
To humans, this chemical also has a narcotic effect so that they become sleepy and less likely to struggle. The ants then take the sleeping prey back to their nest to feed to the ant larvae.
Sources & references used in this article:
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Predation on Spider Mite Eggs by the Western Flower Thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), an Opportunist in a Cotton Agroecosystem by PJ Trichilo, TF Leigh – Environmental Entomology, 1986 – academic.oup.com
Spectral response of cotton aphid–(Homoptera: Aphididae) and spider mite–(Acari: Tetranychidae) infested cotton: Controlled studies by D Reisig, L Godfrey – Environmental entomology, 2014 – academic.oup.com
Natural Products: Repellency and Toxicity of Wild Tomato Leaf Extracts to the Two-Spotted Spider Mite, Tetranychus urticae Koch by GF Antonious, JC Snyder – Journal of Environmental Science and …, 2006 – Taylor & Francis
Effects of fenvalerate and azinphosmethyl on two‐spotted spider mite and phytoseiid mites by DR Penman, RB Chapman… – Entomologia …, 1981 – Wiley Online Library
Remote sensing for detection of cotton aphid–(homoptera: aphididae) and spider mite–(acari: tetranychidae) infested cotton in the San Joaquin Valley by D Reisig, L Godfrey – Environmental entomology, 2006 – academic.oup.com
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