Anatomy of a Spider

Spiders have 2 body segments, 8 walking legs, a pair of fangs, a pair of pedipalps and usually 4 pairs of simple-lens eyes, which provide superb night vision. They also have 2-8 spinnerets from which is produced a liquid protein which hardens on contact with air (often to make a web). However, unlike insects they do not have antennae or wings.

The legs, fangs and pedipalps are attached to the first body segment, the cephalothorax.

Each leg has 6 joints (so a spider has 48 knees!) and lots of sensory hairs.

Almost all spiders have venom glands and inject poison into their prey down a hollow pair of fangs, aka chelicera.

The pedipalps, vary in length and in some spiders can be leg-like and used to manipulate prey. They are sensory organs and in male spiders the pedipalps are also used for insemination.

The second body segment, the abdomen contains the intestines, heart, silk glands, lungs and ovaries or sperm receptacles.

At the rear end of the abdomen, the spinnerets excrete different types of silk, from sticky to non-sticky to extra fine, depending on what the spider requires at the time. Spider silk is more durable and elastic than the strongest man-made fiber, Kevlar, which is used to fill bulletproof vests!*

Spiders have a chitinous** exoskeleton, which they shed as they grow.

*Fritz Vollrath, an evolutionary zoologist at the University of Aarhus in Denmark (live science.com)

**Chitin - a nitrogen-containing polysaccharide, related chemically to cellulose, that forms a semitransparent horny substance and is a principal constituent of the exoskeleton, or outer covering, of insects, crustaceans, and arachnids.

Philosophy Friday
Humanity is like an enormous spider web, so that if you touch it anywhere, you set the whole thing trembling…
Frederick Buechner