I don't know the types of ants you have in your country, but most ants are not directly harmful to plants. They can, spread infestations of aphids, which then harm plants (think of them as farming them).

As for fire ants biting and stinging, yes, they do bite, but only so they can get a better stab with their stinger.

Black ants that bite, up north? Could be carpenter ants (commonly called bull ants).

Not all ants are bad. In fact Schomburgkias need them to pollinate them

This is the main reason to keep the ant population under control. The ants themselves rarely harm orchids; they do however farm insects that do. The aphids and mealy bugs produce the honeydew substance they are interested in and thus there is a symbiosis of which they are taking advantage.

Primarily you want to prevent a colony from moving into the plant. But a stray or two is only a concern as to alert you to examine the plants' media of your collection and throw down another trap or two.

Carnivorous plants may also be an option :evil:

We get red fire ants ! They are rather bigger and do not leave the buds easily.
You know the stem is so tiny and that can't stand several bites. The night time slugs eat them.

Cinammon! Great! I don't know it keeps ants away as well. Ants are the reason why developing buds of my dendro and phals gets dried up and drop.

I get the small black ants in my potted plants - lots of watering and a few ant stakes usually help out quite a bit. there is a gel to get if you can find it - its called Combat, and very difficult to find. basically its the same stuff the pest control companies use. the ants take the gel to their nest and start killing off the colony.

the worst ant invasion we had was when a queen set up house in our car! - called it the antmobile for ages...

hmm pitcher plant on the same pot with the orchid. would that be fine?

are ants afraid of cow dung?