Ants will not hurt your cat. Cats won't sit still to let that happen. I don't think borax is going to hurt your cat either, but I would use the same solution and wipe down the outside of the window and perhaps the wall beneath it to disrupt the ants' scent trail to the food source they now know about.
If you do wipe down the outside of your house near the window where they came in, you might add EITHER bleach or vinegar - NOT BOTH as they can react badly. Either one should knock the pheromone trail off.
There is no point in trying to control the ants if they are coming in from outside. Best to change the place you put your catfood for a while and keep the area clean and free of food sources. The ants will find something better to gorge on.

Thanks Mark for your reply. I have been told since posting, that they were pissants. You got that right!! lol. I didnt think of cleaning around the outside of the window, but will do that as well. The catfood is now locked up tight in tupperwear and isnt exposed unless I take it out to feed the cat then lock it right back up. One encounter was more then enough. I havent seen them since *knock on wood*

The term "pissant' is essentially meaningless, applied to a wide variety of ant species. Very likely, a more accurate name for what you have is "thief ants" (Solenopsis species), which are diminutive relatives of the infamous fire ants of the Southeast, but too small to deliver a painful sting like their larger relatives. Still a serious annoyance in your pet food, though!

I recently had the same problem with the ants in my cats' food, only mine were tiny black or dark brown ants. This was my first experience with them after many, many years living with cats! I cleaned the area really well with Simple Green and moved the cat dishes to another room. So far, so good. I haven't seen any more ants in the area!

Here is an explanation for the name 'pissants' from the web.
Diana

Odorous Ants, Piss Ants, Sugar Ants

In the United States, any small or tiny ant that infests a home is often labeled as a Pissant or piss ant. An actual Pissant is an ant that lives in certain European forests and gets its name from the odor produce by its nesting material - pine straw and pine needles. Middle English pissemyre : pisse, urine (from the smell of the formic acid that ants secrete); piss + mire, ant (probably of Scandinavian origin; akin to Danish myre).

Small indoor ant infestations (those commonly called piss ants, sugar ants) can be any of a variety of small ants. Pharaoh Ants, Ghost Ants, White-Footed Ants, Odorous House Ants, Crazy Ants and other small ants are often the number one pest control problem in certain areas of the country. On the west coast of the United States, Argentine Ants are a major concern.

Each ant species has different characteristics that must be examined before deciding on pest control methods. Ant baits are very attractive pest control tools to many people for various reasons. If an ant population will accept a bait, insecticide sprays and dusts are not always necessary.

We to have a problem with these tiny ants in our home Ant baits dont seem to do squat for them . Has anyone out there got a solution as to how to rid our home of them ,other than using insecticides that is , We bon't like to use them because we have three cats ,our family (s)

I had them for years EVERYWHERE! Some of the better ant baits helped for awhile -- the kind I bought from an exterminator. But after I started spraying diluted orange oil around the areas where the ants were seen they disappeared. What a relief!

The orange oil sold in grocery stores already diluted is not strong enough. I bought the non-diluted at a garden supply store and mixed it according to directions on the bottle, or maybe a little stronger. Haven't seen an ant in the house for months!