10 Fascinating Facts About Spiders

Face of jumping spider

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Some people love them, and some hate them. Regardless of whether you're an arachnophile (a person who loves spiders) or an arachnophobe (someone who doesn't), you'll find these 10 facts about spiders fascinating.

Their Bodies Have Two Parts

All spiders, from tarantulas to jumping spiders, share this common trait. The simple eyes, fangs, palps, and legs are all found on the anterior body region, called the cephalothorax. The spinnerets reside on the posterior region, called the abdomen. The unsegmented abdomen attaches to the cephalothorax by means of a narrow pedicel, giving the spider the appearance of having a waist.

Most Are Venomous

Spiders use venom to subdue their prey. The venom glands reside near the chelicerae, or fangs, and are connected to the fangs by ducts. When a spider bites its prey, muscles around the venom glands contract, pushing venom through the fangs and into the animal. Most spider venom paralyzes the prey. The spider family Uloboridae is the only known exception to this rule. Its members do not possess venom glands.

Some Even Hunt Birds

Spiders hunt and capture prey. The majority feed on other insects and other invertebrates, but some of the largest spiders may prey on vertebrates such as birds. The true spiders of the order Araneae comprise the largest group of carnivorous animals on Earth.

They Can't Digest Solid Foods

Before a spider can eat its prey, it must turn the meal into a liquid form. The spider exudes digestive enzymes from its sucking stomach onto the victim's body. Once the enzymes break down the tissues of the prey, the spider sucks up the liquefied remains, along with digestive enzymes. The meal then passes to the spider's midgut, where nutrient absorption occurs.

They Produce Silk

Not only can all spiders make silk, but they can do so throughout their lifecycles. Spiders use silk for many purposes: to capture prey, protect their offspring, reproduce, and assist themselves as they move, as well as for shelter. However, not all spiders use silk in the same way.

Not All Spin Webs

Most people associate spiders with webs, but some spiders don't construct webs at all. Wolf spiders, for example, stalk and overtake their prey, without the aid of a web. Jumping spiders, which have remarkably good eyesight and move quickly, have no need for webs, either. They simply pounce on their prey.

Male Spiders Use Special Appendages to Mate

Spiders reproduce sexually, but males use an unusual method to transfer their sperm to a mate. The male first prepares a silk bed or web, onto which he deposits sperm. He then draws the sperm into his pedipalps, a pair of appendages near his mouth, and stores the semen in a sperm duct. Once he finds a mate, he inserts his pedipalp into the female spider's genital opening and releases his sperm.

Females Eat Males

Females are typically larger than their male counterparts. A hungry female may consume any invertebrate that comes along, including her suitors. Male spiders sometimes use courtship rituals to identify themselves as mates and not meals.

Jumping spiders, for example, perform elaborate dances from a safe distance and wait for the female's approval before approaching. Male orb weavers (and other web-building species) position themselves on the outer edge of the female's web, and gently pluck a thread to transmit a vibration. They wait for a sign that the female is receptive before venturing closer.

They Use Silk to Protect Their Eggs

Female spiders deposit their eggs on a bed of silk, which they prepare just after mating. Once a female produces eggs, she covers them with more silk. Egg sacs vary greatly, depending on the type of spider. Cobweb spiders make thick, watertight egg sacs, while cellar spiders use a minimum of silk to encase their eggs. Some spiders produce silk that mimics the texture and color of the substrate on which the eggs are laid, effectively camouflaging the offspring.

They Don't Move by Muscle Alone

Spiders rely on a combination of muscle and hemolymph (blood) pressure to move their legs. Some joints in spider legs lack extensor muscles entirely. By contracting muscles in the cephalothorax, a spider can increase the hemolymph pressure in the legs, and effectively extend their legs at these joints. Jumping spiders jump using a sudden increase in hemolymph pressure that snaps the legs out and launches them into the air.