Black widow spider in a container of grapes at a Milwaukee supermarket.

"I saw the legs moving frantically... I've seen bugs on fruit before, and I thought, 'That is a very big spider.' Nothing I'd ever seen before."

Black widow spiders, which build webs in grape vineyards to capture insects, have occasionally been found in supermarket grapes since the mid-1990s. That's when growers came under pressure to cut back on insecticide use because of high levels of pesticide residue on grapes...

Reports of black widow spiders on grapes have popped up in the past few months in Missouri, Michigan and Minnesota.