Ants.

Agreed - while ants will not usually "destroy" an orchid (although they will feed on the honeydew from the inflorescences and may damage some plant parts and or roots - they will actively establish a nest in orchid pots - and once you water them what seems like MILLIONS will come out...

I have very good luck using TERRO liquid ant baits - which are non toxic - and it kills all the ants, including the queen. It comes in a liquid that you can either place on little bits of paper or in pre- made feeding stations.