Spiders help control insect pests in gardens and parks and among field crops. Some mites eat other mites and are used to control the populations of mites that harm crops. However, many ticks and mites act as parasites on people and other animals and spread diseases. Despite their reputation, only a few
SMOOTH AS SILK?
Spider silk is a liquid protein played out as dry fibers through spigots mounted on six abdominal faucetlike structures called spinnerets. The spinnerets form a pump-and-valve pressure system that allows spiders to change the thickness, strength, and stretchiness of their silk. Certain kinds of spiders, called cribellate (KRIB-uh-layt) spiders, have a special plate, called the cribellum, that produces webs made up of wooly strands of silk that are sticky, like Velcro. Ecribellate (EE-krib-uh-layt) spiders lack this plate and produce webs that are tacky by virtue of glue droplets strung out like pearls along the silken strands.
spiders and scorpions have venoms strong enough to harm people. The venomous bites and stings of such spiders and scorpions are dangerous to humans, especially young children, elderly persons, or people who are already in poor health.
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