Quiz: Spider bites and insect stings

Nearly all 20,000 species of spiders are venomous. But the fangs of most spiders are too tiny to penetrate human skin.

The venom in a black widow bite causes a reaction throughout the body, not just near the bite. Symptoms can include muscle and abdominal cramps, plus nausea, vomiting, chills and fever. If you develop these types of symptoms a few hours after a spider bite, get medical help immediately.

Black widow spiders are found in southern Canada, throughout the United States and in Mexico. A black widow's body is about half an inch long (1 centimeter, or cm) with legs stretching out another inch (3 cm).The shiny black body has an orange hourglass on the underbelly.

Most common in the southern and central sections of the United States, brown recluse spiders live in dark, quiet places — such as woodpiles or little-used closets. Some people have no reaction at all to a brown recluse bite, while others develop a painful, ulcerating sore. In the most serious reactions, the tissue around the bite site dies and sloughs away or requires surgical removal.

Brown recluse spiders are about half an inch long (1 centimeter, or cm) with legs stretching out another inch (3 cm). These spiders are golden brown with a dark violin shape located on top of their backs. The violin's neck points toward the rear of the spider.

Mammals, including humans, expel carbon dioxide and lactic acid when they exhale, and mosquitoes can home in on them from as far away as 100 feet (36 meters).

Rocky Mountain spotted fever and Lyme disease are both carried by ticks. Mosquitoes carry various forms of viral encephalitis, which causes brain inflammation and swelling. In the United States, the four most common forms of encephalitis are:

• Equine encephalitis
• La Crosse encephalitis
• St. Louis encephalitis
• West Nile encephalitis

The most severe allergic reactions (anaphylaxis) to bee stings can be life-threatening. If you're allergic to bee stings, ask your doctor to prescribe a self-injection kit containing epinephrine (ep-ih-NEF-rin). Keep the kit with you whenever you might be exposed to bees. If you're stung, remain calm and inject yourself with the epinephrine, following your doctor's instructions. Then seek emergency medical care.

If a bee has never stung you before, you may not know whether you're allergic. Anytime you develop breathing problems, swelling of the lips or throat, faintness, confusion, rapid heartbeat or hives after a sting, seek emergency care.

Fire ants, typically found in the southern parts of the United States, tend to bite their victims to anchor themselves and then sting repeatedly as they move their bodies in an arc around the bite site.

If the stinger remains in your skin, remove it immediately and then use an ice cube to reduce the pain. If you've ever had a severe allergic reaction to fire ant venom, carry an epinephrine kit when you may be around fire ants. Your doctor may suggest taking allergy shots to reduce the likelihood of a serious reaction in the future.

Chiggers are tiny, red bugs that you can often see with a magnifying glass. Sometimes you can see them in the center of pimples that form around an unscratched bite. They insert a mouth tube into your skin, inject enzymes and feed off the liquefied cells. The enzymes cause localized redness, swelling and itching.

Chiggers remain attached to your skin for only a few days before dropping off. Your best bet for over-the-counter relief from itching comes in the form of creams or lotions containing 1 percent hydrocortisone. Oral antihistamines also may help.

Remove embedded ticks with fine-tipped tweezers. Grab the tick firmly and as close to the skin as possible. Pull the tick's body away from your skin. Don't be alarmed if the tick's mouthparts remain in the skin. They will be expelled on their own. Don't use oil, petroleum jelly, kerosene or a smoldering match to remove a tick because these methods may cause it to inject disease-causing fluids into the wound.

Tick bites can cause a variety of illnesses. A correct diagnosis often depends on the geographic location, the season, the type of tick, and how long the tick was embedded in your skin. Lyme disease is one of the most commonly reported tick-borne illnesses.

The exact time may vary, but generally a tick carrying the bacteria that cause Lyme disease must latch onto your skin for 48 hours before transmitting the disease to you. This means you can reduce your risk by checking yourself for ticks as soon as possible after you've been in the woods, where they thrive.

The stings of most North American scorpions require no special treatment because they rarely cause serious problems. However, bark scorpions — found in New Mexico, Arizona and parts of California — are much more toxic. A bark scorpion sting can cause abnormal head, eye and neck movements; increased saliva production; sweating and restlessness.