I have been seeing a LOT of small black ants on my hive, marching up one corner and going right in under the outer telescoping cover. The other day I also noticed them bringing their "stuff" with them (larvae, suitcases, etc.) and sneaking in under the metal covering that makes the roof of the outer cover - when I touch the top, I can tell there's a small space between the wood and the metal. So today I took action. I bought 4 lengths of PVC pipe, maybe 3 or 4 inches in diameter and 3 inches tall. I set those posts into shallow dishes which I filled with cooking oil. With the help of my husband, we lifted the hive up and placed these posts underneath the 4 corners of the hive on the stand, so that the hive is now up on stilts which, presumably, will keep the ants from climbing up from the ground. I also took some caulking and caulked around the metal roof so that the ants won't be able to get in or, unfortunately for them, get out.
Hope this works. Very pesky those ants.