The Two Parts of a Spider

Cephalothorax

• The cephalothorax is the front part of a spiders body. The cephalothorax is usually smaller than the abdomen and contains the leg joints, eyes, pedipalps and mouth parts -- called chelicerae -- of the spider. The cephalothorax contains the main sensory organs of the spider.

Abdomen

• The abdomen is the large, round, rear portion of a spider. The abdomen has six finger-like structures on the anterior portion called spinnerets. The spinnerets help delicately lay down the silk produced in the abdomen. The spider abdomen contains life support organs, including the digestive tract, lungs and reproductive organs.

Pedicel

• The cephalothorax and abdomen are connected by a thin structure called a pedicel. The pedicel is only found in spiders and not other arachnids, such as ticks or scorpions. The pedicel serves as a flexible connective tunnel through which the nerve cords, intestinal track and blood vessels pass between the two parts of the spider's body. The pedicel allows the spider to move the abdomen independently from the cephalothorax, making it easier for it to spin complex webs.

Development

• Spiders hatch from small eggs fully developed. The exoskeleton of young spiders is often soft and may appear pale. Spiders shed their exoskeleton through a process called molting. Spiders literally crawl out of their old skin, leaving behind the shell of their previous exoskeleton. Spiders never stop growing and continue to molt periodically until they die.