Diatomaceous earth is the fossilized shells of tiny marine creatures called diatoms. These shells are mined from deposits in the earth and processed into a fine powder used as an insecticide. Diatomaceous earth has sharp edges that cut into the the outer coatings of insects and absorb moisture. This dessication of the exoskeleton causes insects to die. Diatomaceous earth must be kept dry to remain effective, according to the Living With Bugs website.
Boric acid is made from borax, a naturally occurring mineral that is mined and processed for use. Boric acid acts as a stomach poison when consumed by ants, according to BeyondPesticides. It is slower-acting than other types of insecticides, but is safe for use around humans and pets when used as directed. Commercial ant baits often contain forms of borax mixed with a sweetener to encourage the ants to bring it back to the nest where it will kill other ants.
Though it may seem strange, you can use ordinary instant grits as a pet-safe pesticide that won't harm pets. Cooked grits are perfectly safe for people or pets to eat, but when ants eat uncooked instant grits, the moisture in their stomachs make the grits hydrate and swell, which then kills them. These instant grits are formulated to absorb moisture quickly, and this provides the lethal effect, according to Environmental Health & Safety Online. Mixing the grits with something sweet like molasses or honey will encourage the ants to consume it quickly. You also can sprinkle the instant grits on ant mounds or around points of entry into the house.
Another simple, homemade solution to killing ants in a nest on your property is to pour a large pot of boiling water on them. For this method to work, you must follow the ants back to their nest. Adding some cayenne pepper or citrus oil to the water will intensify the effect. Continue pouring the boiling water onto mounds daily until all ants are dead. This method will not harm pets in any way.