Spiders produce silk, which is secreted as a liquid through the spinnerets and hardens on contact with air. Many different types and textures of silk are produced by various species. The silk is used to construct snares or webs, egg sacs, drag-lines, and ballooning threads. Many spiders produce web snares of various designs to trap prey, and all construct a silk sac in which to deposit their eggs. Some egg sacs are quite elaborate, with four or more distinct types and many layers of silk, while others have only a few individual strands.
Most species attach drag-lines of silk to the substrate at intervals wherever they go.
This is why spiders always seems to have a silk thread to hang by if knocked from their perch. These young spiders climb to a high point and release silk strands until the drag from the wind is sufficient to support their weight. Then, they release their hold and sail away, sometimes for considerable distances. Life History Spiders reproduce by laying eggs that hatch into spiderlings. The increase in size from one growth stage to the next occurs between the time the old skin is shed and the new one hardens.