They are usually described as tiny flies, bees or flying ants but in fact are small parasitic wasps that are about the size of a fruit fly or large gnat. There are literally hundreds of parasitic wasp species and some of them specialize in parasitizing beetle larvae including wood boring beetles. They can be seen going in and out of existing beetle emergence holes looking for live beetle larvae to lay their eggs on. People assume that these insects are actually burrowing into the wood since they often see frass or sawdust being pushed out of
the holes they’ve entered. In their search for live beetle larvae the wasps clean out the tunnels by kicking the frass out of existing beetle emergence holes. Since the wasps can’t tell if the hole was made recently or ten years ago they tend to clean out every hole they can find. Since they do not consume wood none of the borate treatments have any effect on them. In this respect they are similar to carpenter bees.
Some people get excited when they see 20 or 30 of these wasps flying around their log walls but they are harmless and do not sting. They do no damage and are, in fact, beneficial insects since they reduce the population of wood boring beetles. Most of their activity occurs in the hot, summer months. Once the weather starts to cool a bit they usually disappear. If you are really upset by these insects you can spray your walls with Ortho Home Defense, Spectracide Bug Stop or similar products but being somewhat adverse to the broadcast use of contact pesticides we believe the best solution is to just ignore them.