★★★★★
For Flea Prevention: start at the head of the cat or dog and go to the tail with a line of the DE from the bottle. Rub it in. Do this once a week during flea season. Once a month during off season. DE is not a cure-all in my opinion, it is part of the prevention. Again, you don't want you or your pet breathing this stuff in so, the environment for application should be very calm. Wrestling a cat and trying to apply this stuff would kick up the dust. It is non-toxic but you don't want it in you or your pets lungs. If your cat is a mixed martial arts specialist, try something else. I also use an old rouge brush - dab it on the back of the neck of one cat who comes by occasionally.
For Ants: Try to locate the entry point of your ant infestation and squirt a small amount of DE in the corners of the house where they are coming in. The ants or bugs will die with contact of this stuff. I had ants coming into certain parts of the house...I watched them and figured out where they were coming from. Problem solved. No need for pesticides. Remember, if you apply DE to the outside of the outside, it will have to be reapplied if there is moisture (rain) or very high humidity. It will wash away.
By the way, I am asthmatic - DE has not bothered me at all when used in this manner. If I had carpets, a respiratory compromised person or small children, I personally would not put it on the floors. This is just my opinion.
Good Luck!