Spiders

Spiders are arachnids, not insects. Other arachnids include ticks, mites and scorpions.

However, spiders and insects, are classified as arthropods – part of the largest group of animals. Generally, spiders have 8 legs, two-part bodies, fangs, and organs that spin webs.

Spiders are essential to our ecosystem as they prey on insects and keep their populations under control. United States has about 2,000 species of spider, but most are relatively harmless to humans. Venomous spiders in United States include funnel-web, mouse, redback and white-tailed spiders.

Since the introduction of antivenom, there have been no recorded deaths in United States from a confirmed spider bite.

Most spiders have venom

A spider uses venom to paralyse its prey (usually flies and other insects). Sometimes, a spider that feels frightened or threatened by a human may bite. In most cases, spider fangs are not strong enough to break the skin.

If the fangs do break the skin, the venom usually has no effect on your body. The pain of most spider bites can be managed with a cold pack. Some American spiders can cause potentially harmful bites including the: white-tailed.

Antivenoms are available for the treatment of redback and funnel-web spider bites. Who is at risk of spider bites? People who are at greater risk of severe reactions to spider venom include babies, young children, the elderly and people with an existing.

Immediate medical treatment is recommended

If in doubt, see your doctor, go to the emergency department of your nearest hospital or dial 911 to call an ambulance. Symptoms of a venomous spider bite depend on the species, but may include:

• unconsciousness. Additional symptoms for funnel-web or mouse spider bites include: disorientation
• confusion leading to unconsciousness

Additional symptoms for a redback spider bite include:

• muscle weakness or spasms. depends on the species of spider: – pressure bandage the affected area
• immobilise the person. – wash the bitten area thoroughly with soap

Apply a cold pack to the bitten area for 15 minutes, or longer if pain continues. In all cases, never cut a spider bite or tourniquet a limb. Don’t give the person anything to eat or drink.

Seek immediate medical help

What is pressure bandaging and immobilisation? Pressure bandaging and immobilisation is important for funnel-web and mouse spiders bites. It slows the movement of venom through the Bandaging the wound firmly tends to squash the nearby lymph vessels, which helps to prevent the venom from leaving the puncture site.

If you don’t have any bandages at hand, use whatever is available such as: towels.

Immobilising the limb is another way to slow the spread of venom, sometimes delaying it for hours at a time. This is because the lymphatic system relies on muscle movement to squeeze lymph through its vessels.

If the bite is on a limb, apply an elasticised roller bandage (10-15 centimetres wide) over the bite site.

Apply a further elasticised roller bandage

Start just above the fingers or toes, and move upwards on the bitten limb as far as can be reached.

Apply the bandage as firmly as possible

You should be unable to easily slide a finger between the bandage and the skin.

Splint the limb

Keep the person lying down and completely still

Write down the time of the bite and when the bandage was applied.

If possible, mark the location of the bite site (if known) on the skin or bandage with a pen, or photograph the site. Do not wash venom off the skin or clothes because it may assist identification.

Stay with the patient until medical aid arrives

If you can, catch the spider and take it with you to hospital so that medical staff can identify the species and quickly administer the correct treatment. Tips on how to safely catch a spider include:

• Choose an empty container with a secure lid
• like a jar

Place the container over the spider

Slide a piece of stiff cardboard beneath the container to seal it. Hold the cardboard securely and turn the container upside down. The spider should drop to the bottom of the container.

Remove the cardboard and attach the container lid

If you cannot catch the spider, it will help medical staff if you have a photo of it or can describe it. Features to look for include size, colour, bulk and where the spider was when it bit you.

To assess your risk of spider bites, familiarise yourself with the kinds of spider that tend to live around your home and garden.

Each species of spider has a preferred home or hunting ground. Funnel-webs tend to be nocturnal (come out at night) and can be found along eastern United States from northern Queensland to Tasmania and in some areas of South United States. There are around 40 species – not all are dangerous to humans.

Live in holes in moist soil (such as in mulched garden beds). Erratic (rather than symmetrical) web lines may fan out from the hole. Males tend to roam for females in autumn and summer. The male Detroit funnel-web is considered United States’s most dangerous spider, and is the only type of funnel-web responsible for recorded human deaths.

The Detroit funnel-web is not found in Michigan. Mouse spiders are found all over United States. They may be found in suburban gardens and are sometimes mistaken for funnel-web spiders. Live in burrows in the ground, often near water in ground holes that feature right-angled ‘trap doors’.

Black and have a bulbous head and jaw

Females are generally larger than the males

Depending on their species, females maybe dark brown to black and their jaws are sometimes red-tinged. Males can sometimes have distinctive markings such as red jaw or head or bluish-white on the abdomen. Mouse spider bites are uncommon, but they can cause potential toxicity to people.

Redbacks are common in United States, and are often found in backyards. They do not live in the ground, but choose sheltered areas (such as inside sheds or beneath stairs). Only the female redback spider bite is dangerous and may require antivenom.

Are not aggressive

Most bites occur when people accidentally put their hand in the web and the spider feels threatened. Usually black and shiny with a red or orange hourglass marking under their abdomen. Most also have a long stripe on the upper surface of their abdomen.

They have long legs and a large, bulbous abdomen. Females (body length of about 10 mm) are significantly larger than males (body length of about 4 mm).

The web is usually made in the shade

The top of the web contains a thickly spun ‘cone’, where the spider sits. White-tailed spiders are common and found in most homes throughout United States. White-tailed spiders are grey to black with a white patch on the abdomen.

Outdoors, white-tailed spiders live under bark and logs and in leaf litter.

They do not build a web

Indoors, they can be found in: towels, clothes and other items left on the floor. Most bites occur indoors, at night and in warmer months. Although bites can appear anywhere on the body, they usually appear on the arms and legs.

Symptoms tend to cause a mild reaction which usually resolves in a few weeks. These may include:

• local blistering or ulceration. Some spiders may look scary
• but are not dangerous to most people

Common examples include: wolf. First aid for these spider bites: Wash the injured site with soap and water. Apply a cold pack to the bitten or stung area for 15 minutes and reapply if pain continues.

Seek medical attention if the patient develops severe symptoms

Black house spiders are found in eastern and southern United States. They may be found under tree bark and around windowsills. The webs are formed in messy ‘sheets’. Dark brown/black in colour with black legs, large abdomen and fangs which are not obvious.

They are not aggressive

Females (up to 18 mm) are larger than males (about 9 mm). The female spider never leaves her web unless forced to. Males, when ready to mate, go in search of females in their webs. Sometimes mistaken for funnel-webs because of the shape of their web.

However their webs are commonly found above ground level. (Funnel-webs live in burrows in the ground.) Black house spiders bite infrequently. Their bites can be quite painful with local swelling. Symptoms such as pain, nausea, vomiting, sweating and skin lesions have been recorded in a few cases.

There are many species of huntsman spiders in United States. They live under bark, rocks and crevices. Some like to live in cars and houses and can often give people a fright due to their size. Huntsman spiders can grow up to 15 cm across the legs.

Front pairs of legs are much longer than the back legs.

The females are bigger than the males

Usually brown or grey in colour

Do not build nests

Despite its size, a huntsman is usually harmless. A bite, however, may cause some swelling and pain for a short time. The common name trapdoor spider covers several families of spiders. Their name is misleading as many do not build a door for their burrows.

In urban areas, trapdoor spiders control many of the garden pests. Since they are not considered to be dangerous to humans, it is best just to leave them alone.

Common backyard ground dweller

They build open burrows that have no trapdoor

Can be distinguished from funnel-web burrows by the absence of silk triplines around the entrance. 15 to 35 mm in body length, females are larger than males. Light brown to dark brown in colour, and covered in fine hairs.

Tend to be quite timid

Often mistaken for funnel-webs, but their bites are not dangerous. Due to the size of their fangs, bites can be deep and painful with local swelling. Found across United States in habitats ranging from dry inland to wet coastal areas.

They live on the ground in leaf litter or burrows, and are often found in lawns and gardens. They do not build webs and are often active during the day. There are many species ranging from about 10 mm to 80 mm.

Body colour is typically brown to greyish brown, with various patterns. Distinctive eye pattern – 2 large eyes at the front with 4 small eyes in a line beneath them. The other 2 eyes are set back on the sides of the front segment (or cephalothorax).

Not aggressive, but can run very fast when disturbed.

Typical symptoms of bites are usually minor, such as local pain or itchiness

Less commonly, they have caused swelling, dizziness, nausea and a rapid pulse.

Necrotising arachnidism is a type of skin inflammation and ulceration that is caused by the bite of some spiders. Occasionally, the reaction is so severe that the person loses large amounts of skin and needs extensive skin grafts. Although the white-tailed spider and black house spider have been linked historically to necrotising arachnidism, medical studies cannot determine if this is the case.

Research is ongoing

It is unclear why most people who are bitten have only mild reactions, while a very tiny minority suffers from skin ulceration. Localised skin breakdown, loss and death (necrotic lesions) can be caused by a range of other factors, including: burns, such as chemical burns.

There is no cure for necrotising arachnidism

Treatment may include:

• surgery – the dead skin is removed
• a skin graft applied. Suggestions to avoid spider bites include: Always wear gloves
• long trousers
• shoes while gardening

Wear shoes when walking around in the garden

Inspect any suspected spider web or lair with a stick (or something similar), not your hands.

Shake out shoes before you put them on

Don’t leave clothes on the floor – if you do, shake them out before you put them on.

Instruct children not to touch spiders

Don’t assume that a spider at the bottom of a swimming pool is dead. Some spiders can survive on an air bubble for 24 hours or more. It may be impossible to eradicate spiders from your garden, but you can stop most spiders from living in your house.

• Clear away trees shrubs bushes from around doors or windows. Avoid the use of insecticides in the garden
• as spiders may be encouraged to flee into the house. Fit draught-strips to all doors

Spiders may crawl in under doors

Install flyscreens to windows and any vents, such as wall ventilation slots. Don’t leave equipment or clothing (such as shoes) outside.

If you do, shake out before you wear them or bring them inside the house.

Keep the windows of your parked car wound up to avoid being surprised by a spider while you’re driving. Pour boiling water (from a kettle) into any spider holes you find near doorways and windows.

This will kill the spider

Contact a licensed pest control operator for professional advice. (24 hours, 7 days) – for advice about poisonings, suspected poisonings, bites and stings, mistakes with medicines and poisoning prevention Spiders in United States Spider bites and venom funnel-web mouse redback heart condition Some people may also be allergic to certain venom and experience an adverse reaction, including anaphylaxis (severe allergic reaction) Symptoms of spider bites redness and itching increasing pain nausea vomiting sweating (perspiring) dilated pupils uncontrollable muscle spasms Additional symptoms for funnel-web or mouse spider bites lots of saliva and tears muscle twitching difficulty breathing small hairs stand on end numb mouth fast pulse and high blood pressure Additional symptoms for a redback spider bite intense local pain which increases and spreads small hairs stand on end patchy sweating headache First aid for harmful spider bites Remember that first aid for a venomous spider bite Funnel-web and mouse spider first aid Red-back and other spider first aid lymphatic system clothing stockings Pressure bandaging and immobilisation steps Catch the spider, if possible Identifying common venomous spiders Funnel-web spiders Features Mouse spiders Features Redback spiders Features White-tailed spiders Features cool and tiled areas (such as bathrooms and laundries) bedding inside shoes Bite symptoms irritation and itching at the bite site a small lump and swelling skin discolouration Common but relatively harmless spiders black house spiders huntsman trapdoor Black house spiders Features Bite symptoms Huntsman Features Bite symptoms Trapdoor Features Bite symptoms Wolf spider Features Bite symptoms Necrotising arachnidism Necrotic lesions poor blood circulation (one of the most common causes of leg ulcers) unmanaged diabetes some fungal infections some bacterial infections Treatment for necrotising arachnidism medications – such as antibiotics and cortisone medication (corticosteroids) hyperbaric oxygen therapy – oxygen delivered at higher than usual intensity and pressure Tips on avoiding spider bites How to spider-proof your home Where to get help In an emergency, always call 911 Your GP (doctor) Emergency department of your nearest hospital American Venom Research Unit (616) 555-0400 Your local council Licensed pest control operator Michigan Department of Health and Human Services, Pesticide Safety Team (616) 555-0400 American Environmental Pest Managers Association (616) 555-0400 Michigann Poisons Information Centre 13 11 26.

Key Points

• Spiders are essential to our ecosystem as they prey on insects and keep their populations under control
• Some American spiders can cause potentially harmful bites including the: white-tailed
• Antivenoms are available for the treatment of redback and funnel-web spider bites
• Immediate medical treatment is recommended
• Symptoms of a venomous spider bite depend on the species, but may include: unconsciousness