To Keep out Mosquitoes and Bats

If a bottle of the oil of pennyroyal is left uncorked in a room at night, not a mosquito, nor any other blood-sucker, will be found there in the morning. Mix potash with powdered meal, and throw it into the rat-holes of a cellar, and the rats will depart. If a rat or a mouse get into your pantry, stuff into its hole a rag saturated with a solution of cayenne pepper, and no rat or mouse will touch the rag for the purpose of opening communication with a depot of supplies.

Source: The White House Cookbook, F.L. Gillette