Introduction to Spiders

Spiders come in many shapes, colors, and sizes, but they all have characteristics in common. We all know spiders have eight legs. What other characteristics make a creature a spider, and not an insect?

 

Physical Characteristics of Spiders

1) Two body sections (an insect has three):

A) A cephalothorax (combination head and thorax), which contains the brain, poison glands, and stomach, is covered by a shield called a carapace.
B) An abdomen contains the heart, lungs, digestive tract, reproductive organs, and the silk glands.

2) Nearly all spiders have four pairs of simple eyes.

3) All spiders have silk-producing spinnerets at the end of the abdomen. (see silk section below)

Behavioral Characteristics of Spiders

1) All spiders are predatory, feeding on other smaller animals. Some spiders, for example, the orb weavers, spin silk webs in which to catch prey. Others, such as wolf spiders and jumping spiders, hunt down their prey.

2) Spiders kill their prey by injecting them with venom from their poison glands. The venom is injected using their fang-like chelicera.

Spider Habitat

Spiders can be found in nearly every conceivable kind of habitat. The limiting factor appears to be the lack of available food to prey upon. Many species live outdoors under natural surroundings and seek shelter in ground litter, vegetation under rocks, or in crevices. Those species that build webs may construct them in vegetation or are associated with human dwellings. A few species, such as the house spider, cellar spider, and brown recluse, have adapted to living inside houses. They take advantage of the protection and warmth that our houses provide. It has been stated that usually we are never farther than about eight feet from a spider during most of our lives!

Life Cycle of Spiders

Male and female spiders mate when they are mature. The female deposits eggs (sometimes up to several hundred) in a silken sac. The young spiderlings emerge weeks later (or the following spring).
Most spiders live for one or two seasons. Males often die shortly after mating, while females of some species may live for years.
As they grow, spiders shed their exoskeleton.

Spider Silk and Webs

A spider's abdomen contains four to seven silk glands that produce the protein fiber. Each type of gland produces a different type of silk (sticky silk, web frame silk, egg sac silk). The liquid silk goes through the spinnerets at the rear of the abdomen. It hardens as it emerges. Spider silk is a very strong substance. The spider uses its claws to handle the strands of silk.

A simple use of a strand of silk is a dragline. The spider lays down a line of silk as it travels, attaching it to things at intervals, to act as a safety line, or a path marker by which it can find its way back.

Another use of a single strand is when a spider, on a tree branch or other high place, lets out a line. The wind catches it and balloons it out, allowing the spider to float down to a new place.

Spiders weave silk webs of several basic shapes. They also use silk to make egg cases, nurseries, tunnel liners, and trapdoors. The basic web types are cobwebs, sheets, funnels, and orb webs.

A cobweb is a tangled mass of fluffy silk that catches insects.
A sheet web (sometimes called a triangular web) is flat with main lines running down the center. When an insect lands on the web, the spider shakes it, causing the insect to struggle and get caught in the strands.
A funnel web is built in the grass. The spider hides at the small end and rushes out and grabs the insects as they come down the funnel.
An orb web is shaped like a circle. The spokes are built first, then the spiral connecting strands are added. Insects fly into the barely visible orb.

Read a Living Museum magazine article on Native American weaving titled "The Gift of the Spider Woman" to learn about the meaning of spiders in Mississippian culture.

Related Activities:
Spider Anatomy & Identification (html) (pdf)
Spider Poem (html) (pdf)
Spider Gorget (html) (pdf)