Ant activity will make the potting mix break down faster, and can make the medium extremely acidic. As Phillip said, some orchids enjoy the company, but I would prefer if they stay away. :)

what should i do then?

I try to keep them out but it is a constant struggle. I use baits and grandules that "kill the colony" to keep them in check, but since most of my collection goes outside for most of the year ants are a constant nuisance. More frequent repotting is a fact of life for me due to bugs and other factors.

In my small nursery i have an ant problem too of slightly larger proportions. I have red fire ants lol. I have them under control by spraying all 10,000 plants with insecticide......As well as the ground under the plants and everything around them and the Mango tree and...and...and........ well it just keeps going

what about soaking the medium with a mix of coffee and nicotiana leaves tea? Tobacco plants have some insecticide/ repellent properties and possibly caffeine too

well it has been raining for an hour now....i'd say i don't have too much of an ant problem for a while now

In the US, most often an ant bite is from a fire ant, and not really a bite, but rather a sting. They can be distinguished by their reddish colour.

Mostly though, fire ants are ground dwellers and not often seen up in potted plants, unless your pots sit on the ground.

If you DO have fire ants, a little Andros sprinkled around the pot (not in it) will eliminate them.

You can eliminate most ants with simple remedies like a spritz with alcohol, or a dusting with cinnamon.

Fire ants bite AND sting. Around here they are impossible to eradicate. You can only hope to relocate them temporarily. :(

i have black ants. and they DO sting or bite or something that hurts! the pot was suspended from a tree

Ants visit orchids because of honey . They sting the buds and they get wilt . Sadness is that.
What I did is I kept a piece of cow dung in between the canes.