The only things I find in prepackaged food is flour bugs. Pretty much unavoidable - eventually you'll get some. Just pick 'em out and cook. Where there is food, you'll find bugs.
Do check your canned items when you buy them though. I recently went to pay for groceries and noticed rust on a can. Discovered that it had passed the sell by date 2 years before. This is a good quality grocery store - it was obviously a lot from the wholesale distributor.