Spiders spin different kinds of silk for many different purposes. There is both sticky and non-sticky silk used in webs (the spider walks on the non-sticky), silk for wrapping up prey, silk for dispersing themselves in the wind, silk used as a safety drag line and silk used for egg sacs.
The egg sacs of different species of spiders are quite distinct, so much so that sometimes you can identify the species of spider that spun the sac. They may be built inside a burrow, under loose bark, in a web, in a curled leaf, suspended on a long line, or in a rock crevice. While some spiders abandon their egg sac, some stay with it, guarding it until spiderlings emerge. Others may carry their egg sac about with them in their jaws or spinnerets until hatching occurs.
The egg sac silk protects the eggs against physical damage and excessive drying, wetting or heating, as well as providing a shield against predators like ants and birds. The average female spider’s egg sac holds about 100 eggs, but some large spiders can produce a sac that holds 2,000 eggs.
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