Diatomaceous earth is an all natural product made from fossilized marine plants that are ground up into a fine powder (much like flour). It has many many uses, but pest control is a major one. We use it when ant hills pop up in our tortoise pens (dump a tablespoon right down the hole), and we use it to eliminate tiny dust mites that many tortoise keepers fight with in their indoor enclosures. Lightly apply it all over the enclosure in a dusting about once a week for a few weeks and those dust mites will be gone - at least for a while! The fine, sharp particles will cut up and dehydrate tiny insects without harming larger animals or tortoises. Ours is human, food grade and is eaten by people and fed to pets for various health reasons.