The World's 30,000 Known Species of Spiders

The world's 30,000 known species of spiders

A) kill more livestock with poisonous bites than any other threat.
B) have to be controlled in order for integrated pest management to work properly
C) are a threat not only to livestock, but also to rural farmers because they nest in sheds where equipment is stored and later retrieved.
D) kill far more crop-eating insects every year than humans do by using chemicals.
E) Are at the bottom of the food chain in agricultural settings and so provide important food for birds that control caterpillar populations.