A wet summer produced a bumper crop of insects for them to eat.
Field Museum entomologist Petra Sierwald says spiders are "eating like kings”, and residents throughout the Midwest are seeing the corpulent arachnids everywhere, from bushes to the windows of high-rise buildings.
Former Chicago window washer Russell Hendericks says he's seen workers drop their tools when spiders crawl on their hands. Hendericks says he had a partner who was petrified by the spiders that would be stuck in his hair after a day's work.
Sierwald says there are 899 known spider species in Illinois, Michigan, Ohio, Wisconsin and Indiana. Most will lay their eggs from now through October and then hibernate or die.