This is tobacco country so it is safe to say that anyone who grew up in Eastern North Carolina is familiar with the ubiquitous tobacco hornworm. Recently scientists have discovered that this caterpillar that feasts on tobacco plants has a very unique defense to deter spiders from having them for dinner. This defense involves the nicotine that the hornworms take in while eating the plants.
Each day the caterpillar ingests six times the lethal dosage of nicotine for humans.
Most of the nicotine they excrete in their waste, but they keep some of it which they breath out of their spiracles (breathing holes) and this halitosis warns spiders that they are toxic. So unless the spider is a 2 pack a day smoker, they will leave the little guy alone.