FASCINATING FACTS ABOUT SPIDERS | Back to Caresheet Index |

:: Fascinating Facts About Spiders

Spiders are quite delicate compared to some of their food, but by using poison the spider can subdue its prey before it has too much chance to fight back. Spiders have two poison sacs -one per fang -muscles around the sacs contract, forcing poison down the hollow fangs and out of the small opening, at the 'business' end.

The spiders front bit (CEPHALOTHORAX) contains its poison glands, brain, stomach and muscles. The stomach works by being stretched wide to 'suck in' food
that has been mashed to a pulp.

The abdomen contains the spider’s heart, lungs, breathing tubes, gut, silk glands, reproductive organs and waste organs. The heart pumps its blood around its body.

The seven-sectioned legs are powered by sets of muscles and blood pressure. At the end of the legs spiders have two or three little 'claws'. In web spinning spiders one of the claws helps to hold on to the web. Hunting spiders can have dense, hairy tufts which help hold their prey -these hairs can be so fine at the ends that they draw up a little of the moisture that coats most surfaces (however smooth), effectively sticking the spiders leg down, which means that these spiders can even climb up glass.

Spiders have poor eyesight (at best 30cm / 12"). Some cave spiders have no eyes at all, relying on other senses, especially the sensitive hairs that cover spiders' bodies. Tasting hairs are spread over the spiders' body and the legs and pedipalpi have hairs that can detect tiny movements in the air.

A spider's eyes are on top and near the front of its head. Different species have different numbers of eyes and the size and position also varies. Most species have eight eyes, arranged in two rows of four each. Other kinds have six, four, or two eyes. Some spiders can see better than others. Hunting spiders have good eyesight at short distances and their eyesight allows them to form images of their prey and mates. Web-building spiders have poor eyesight and their eyes are used for detecting changes in light. The eyes, and their arrangement, can help identify a spider:

• Woodlouse spiders (Dysderidae) have six small eyes set in a circle at the front of the cephalothorax..
• Jumping spiders have two large, main, eyes facing forward (these give a focused image) with small, secondary, eyes which pick up light and movement.
• Money spiders can have their eyes on top of little lobes sticking up from their heads.

Below the spider's eyes is its mouth opening. Spiders eat only liquids because they do not have chewing mouthparts. Around the mouth are various appendages that form a short "straw" through which the spider sucks the body fluid of its victim.

The spider can only eat some of the solid tissue of its prey by predigesting it. The spider sprays digestive juices on the tissue and the powerful juices dissolve the tissue. A large tarantula can reduce a mouse to a small pile of hair and bones in about 36 hours by predigesting and sucking.

Pedipalpi are a pall. of appendages that look like small legs. One pedipalp is attached to each side of the spider's mouth, and they form the sides of the mouth. Each pedipalp has six parts. In most kinds of spiders, the part closest to the body has a sharp plate with jagged edges. The spider uses this plate to cut and crush its food. In adult male spiders, the last part of each pedipalp has a reproductive organ.

Spiders can make (up to) six different types of silk from special glands in their abdomen (spinnerets). Some silk is for wrapping prey, some for spinning sticky webs, some is used to make or line a shelter and (females) make some especially for protecting the eggs.

As soon as a male spider matures, it seeks a mate. The female spider may mistake the male for prey and eat him, but most male spiders perform courtship activities that identify themselves and attract the females. The male of some species vibrate the threads of the female's web, male hunting spiders wave their legs and bodies in an unusual courtship dance, jumping spiders use the coloured hairs on their legs to signal females and male nursery web spiders present the female with a captured fly before mating.

Before mating, the male spider spins a silk platform called a sperm web. He deposits a drop of sperm from his abdomen onto the platform. Then he fills each of his Pedipalpi with sperm. He uses the Pedipalpi to transfer the sperm to females during mating. After mating, the female stores the sperm in her body. When she lays her eggs, several weeks or even months later, the eggs are fertilized by the sperm. Females can continue to lay eggs for many months after mating because of the stored sperm. Usually, the female does not eat the male after mating as is commonly believed.