an orb weaver producing silk spinnerets
the abdomen has no appendages except have been modified form 1 4 (usually three) pairs of short, movable spinnerets, emit silk. each spinneret has many spigots, each of connected 1 silk gland. there @ least 6 types of silk gland, each producing different type of silk.
silk composed of protein similar used in insect silk. liquid, , hardens not exposure air result of being drawn out, changes internal structure of protein. similar in tensile strength nylon , biological materials such chitin, collagen , cellulose, more elastic. in other words, can stretch further before breaking or losing shape.
some spiders have cribellum, modified spinneret 40,000 spigots, each of produces single fine fiber. fibers pulled out calamistrum, comb-like set of bristles on jointed tip of cribellum, , combined composite woolly thread effective in snagging bristles of insects. earliest spiders had cribella, produced first silk capable of capturing insects, before spiders developed silk coated sticky droplets. however, modern groups of spiders have lost cribellum.
tarantulas have silk glands in feet.
even species not build webs catch prey use silk in several ways: wrappers sperm , fertilized eggs; safety rope ; nest-building; , parachutes young of species.
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