Next, the spider will work from the edge of the web toward the center laying down a spiral of sticky threads. A good description of how a spider constructs a web can be found in The Book of Spiders by Paul Hillyard. Spider silk is a protein that is formed as a liquid by silk glands and squeezed out of spinnerets like toothpaste from a tube. The liquid thread hardens as it leaves the spinneret and some types of such thread become stronger than a steel thread of the same diameter. Most of the silk threads in a spider web are multiple strands of fine silk lying alongside each other.
Spiders produce several types of silk from different types of spinning glands.
One type of silk formed by all spiders is the type used for wrapping prey. Another type of silk is used to make the egg sac, and yet other is a sticky type often used as part of a web. However, spiders that do not spin webs do produce silk. Some live in burrows which they line with the silk from their silk glands. Young spiders ride the wind on long silk threads in a process that we call ballooning.