No the borers aren't ants. They are a small flying insect. The larvae live inside the tree's wood and over winter there. When they mature they exit the wood and fly away. It was a couple of weeks after being in the warmth ov the iguana's cage that they decided that spring had come and started showing up.

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Merlin,
What's Life Without A Little Magic!

Oh crap.

So how to get rid of them for sure?

Get rid of everything that could have a remote possibility of harming the ig? The only way to do that is heat the wood to the level just shy of where it turns to charcoal.

Nearly everything on or in that limb will not bother the ig. If you just scrub the limb as Meriln suggested you will be fine. Then just let it sit for a while if you want. If there happens to be a bug hatch from on the limb in the future chances are very good the bugs won't bother the ig but will probably drive you nuts for a day or two until you kill them off. This is a risk you take by wanting to use something that looks natural in a cage.

Another thing you will have to watch for is the wood checking. That is as the uncut limb dries it will dry from the outside in and dry wood is smaller than wet. As the outerlayer shrinkes around the wet inner wood it tends to crack radially so you will end up with a few long cracks from the center of the branch to the edge.

This all comes down to a personal choice and whether you see the benefits of using the branch as out weighing the risks.

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~ Mark