I use the "ant bait" products that are designed to kill the queen.
You can kill and spray all the worker ants all you want but the queen will just quickly replace them in a couple of days.

Place the baits near your orchid pots, or on top of the pots to prevent your pets from playing with the bait.

There are several different brands out there and I will not endorse one over the other. Just read the labels and see which one will work out the best for you.

Since you have pets, get the ones that are encased in a plastic case so that your pets cannot lick or eat the bait inside.

I use Orange Guard and it works well!

A strategically placed nepenthes can be a watery grave for hundreds of ants, although, it will by no means get rid of all of them, but it's still fun. There is nothing better watching a line of ants crawling into a pitcher...never to crawl out again. :)

I like your idea Bob. Lol. Insert evil laugh here.

Can I pour Orange Guard into the soil? I thought you use that around the house?

Before I poured anything into the soil, I'd want to know that the plant will tolerate it. I had ants living in one of my orchids, and I just took it outside, dumped the pot, washed the heck out of the roots, and put the plant in a fresh pot. Then I came back with boiling water and scalded all the eggs, larvae, and pupae off the old pot. The pot cleaned up fine, I'll use it again someday. The ants are wandering around outside, where they are welcome to make a home. There is no remains of their scent trail on the plant - it's in a different pot, and there's no dirt in the old pot. No poisons used, and the plant is fine - blooming now.

I understand that treatment might be tough for a very big plant, but it's quick, clean, and pretty certain.

ewwww, this happened to one of my phals a year or two ago. i tried the baits, setting them around the orchid but i guess those little punkasses had their own little self sufficient colony in the plant, because they didn't even come out and get the food!

i tried soaking the whole pot in water to drown them, and that did nothing.

so i ended up taking the plant out onto the porch and dumping ALL the media out, and drenching all of the roots with RAID ant killer. i was positive it would kill the plant, which would really suck, but having ants in the house sucks evenmore.

then i left it for a day on the porch, in the shade.
after a day, i potted it in all-new media in a new pot. surprisingly that plant has lived AND bloomed twice since!!

sooo, if the other options fail, this might be a last resort. GL.

You're right. A VERY last resort!

Speaking of carnivorous plants, ants loved to die within my Sarrancenias. I had few outside and they would fill up so much they'd keel over. Nepenthes need a lot of humidity and warmth so Sarrancenias may be a better outdoor option.
Gnats love them too.

occassionally I'll get black sugar ants nesting in my orchid's pot. When i heavily water the plants, the whole nest will come screaming out; carrying their eggs and larvae. I usually drench the the plant with Malathion or Diazanon (if you can still find that anymore). I grow in a greenhouse, and ant can be a problem. Ants carry in aphids and scale.

My variation on the drown and kill 'em approach by toyo is to set an ant infested pot in plain water, right up to the pot rim. The ants will scramble out of the medium all over the plant. I then use Safer soap to kill the ants. It usually takes three of four dips to get most of them....in my experience the remaining few, give it up and move back OUT of the gh.

This is time intensive but I've avoided using the heavy duty poisons this way.

Some orchids need ants - the little black ones, not fire ants. http://davesgarden.com/guides/articles/view/1057/

The previous post needs to be ignored. No doubt there are quality symbiotic ant/plant relationships. The article goes on about the varied plant life that enjoy ants. But there is nothing about the fact that not any ant species is a friend. Some are neither friend or foe and could be neutral. But there are ants that will cause tremendous damage.

I've been invaded by several species of invasive non domestic ants. White footed asian, Bahamian crazy ants and others. Came here through the port of Miami. Around 100 miles away.

Some ants are excellent farmers. They bring immobile sucking bugs then eat the secretions. Very harmful to the orchids and a lot more.

The right ants in the right place are fine. But in this modern world of rapid cargo transportation, invasive and harmful plants, animals, and bugs is a big problem getting bigger.