To your surprise, you find a dryer sheet inside, making you wonder who left it and why. According to MassLive, many postal workers intentionally put a heavily scented dryer sheet in mailboxes to keep wasps away, as they frequently build nests there. Questions about dryer sheets' effectiveness persist, especially regarding fungus gnats. Hawx Smart Pest Control notes that dryer sheets might offer brief relief from bugs but are not a dependable or comprehensive solution. Although dryer sheets may offer slight repellent effects, they should not be substitutes for more proven pest control methods.