Those are carpenter ants or termites. You have a problem. They'll eat your wood.

I'd be miffed over contractor importing wood destroying insects to my property. Use garden sprayer to squirt ant and termite killer into holes. Be sure and mix some extra to squirt into contractor's body waste orifice.

Cedar contains chemicals that repels termites, so those are not the issue. Carpenter ants could be the problem. But they don't eat wood - they tunnel through damp wood to build nests.

Make sure your lumber is dry and then give it a waterproof coating to prevent any moisture penetration. As well as to prolong its life.