Venomous bugs

Spiders

“If you want to live and thrive, let a spider run alive!” That is an old English saying that means not killing spiders will bring you good luck. There is also a myth that killing a spider will bring bad weather.

Letting a spider live won’t bring you good luck or good weather. But scientists say there is no good reason to kill a spider. Most spiders will not harm you. They rarely bite. Only 30 of the 40,000 species (kinds) of spiders cause illness when they bite people. The black widow and the brown recluse are two spiders that have painful or deadly bites.

Spiders are important to the balance of nature. Spiders eat mosquitoes and other insects. Spiders help keep insects under control.

ARE SPIDERS INSECTS?

Spiders are arachnids. They are not insects. Daddy longlegs, mites, ticks, and scorpions are also arachnids.

You can tell spiders and insects apart. Spiders have eight legs. Insects have six legs.

The bodies of spiders have two parts. The head and *thorax* (chest) form one part, and the abdomen is the second part. The two parts are linked by a thin stalk called the pedicel. The bodies of insects, on the other hand, have three parts. A spider’s body has a hard outer shell.

Insects have antennae, and most of them have four wings. Spiders do not have any wings or antennae.

HOW BIG ARE SPIDERS?

The biggest spiders are tarantulas. They have bodies that are more than 4 inches (10 centimeters) long. A tarantula’s legs spread out over 8 inches (20 centimeters). The smallest spiders have bodies that are less than 0.04 inch (1 millimeter) long.

HOW DO SPIDERS MAKE WEBS?

Spiders spin webs out of silk threads. The silk comes from glands in the spider’s abdomen.

The glands make a liquid. The liquid goes out through tubes as thin as a hair. The tubes are called spigots. The spigots go to spinnerets on the spider’s abdomen. Dozens of spigots go to each spinneret. The spinnerets are like fingers. They can move to stick silk threads to a wall or wrap *prey* (animals they eat) in silk.

WHY DO SPIDERS MAKE WEBS?

House spiders, garden spiders, and other spiders spin webs to catch prey. Some webs are shaped like funnels. Some webs are flat. Some webs are like a circle. The spiders feel the web vibrate when a fly or other insect gets trapped in the web’s sticky threads.

Not all spiders spin webs, but all spiders make silk threads. Spiders leave a silk thread behind them as they go. They can use this thread to make a quick escape. Spiders use their silk to make nests.

Some spiders use their silk to wrap up captured prey. All spiders are *carnivorous* (meat eaters). They eat insects and sometimes other spiders.

Scientists divide spiders into two groups called web spiders and ground spiders. Ground spiders hunt their prey. Wolf spiders and other ground spiders have long, thick legs. They wait for an insect to come along and then jump on it.

HOW DO SPIDERS EAT?

A spider has special mouthparts called chelicerae. There is a sharp fang at the end of each chelicera. The fang is hollow. The spider stabs its prey with the fang. Poison from a poison gland in the spider’s body goes through the fang and into the prey. Big tarantulas are powerful enough to kill frogs and lizards. Small jumping spiders that live in the tropics can jump a long way to attack prey.

Spiders cannot chew their food. The spider spits juices into the wound made by its fang. The juices start to *digest* (break down) the prey outside the spider’s body. The spider’s stomach has muscles that are powerful enough to suck in the digested prey.

A spider can use its mouthparts for things other than eating. It can use them to carry prey. Ground spiders use their mouthparts to dig tunnels in the soil.

DO SPIDERS HAVE HAIR?

Some spiders have hair on their bodies. All spiders have hairs on their legs. Spiders use their hairs to feel and smell things. Each leg has seven parts with joints between them.

The hairs of many tarantulas have barbs like tiny fishhooks. Tarantulas can brush off their abdominal hairs when they feel threatened. The barbed hairs fly through the air. They cause a burning feeling if they get in your skin or up your nose.

HOW DO YOUNG SPIDERS GROW?

The male spider fertilizes eggs from a female spider. The female makes a silky cocoon for her eggs.

Some spider mothers hide their cocoons and then leave them. Other spiders guard their cocoons until the eggs hatch. Female wolf spiders carry their cocoons on their bodies until the eggs hatch.

Spider eggs hatch inside the cocoon. The young spiders go through different life stages. The first stage is as a white, wormlike larva. After about two weeks, the larva changes into a spiderling. Spiderlings look like grown-up spiders, only smaller.

Spiderlings lose their hard outer shell a number of times as they grow. A new shell takes the place of the old one. This is called molting. Small spider species may molt about 5 times. Some large tarantulas may molt as many as 40 times. The last time a spiderling molts it becomes a grown-up spider.

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