It certainly does give homeowners something to talk about. This insect damages the plant as it feeds - and, as it feeds, the bag gets larger and larger. The larva is a good builder, as it constructs a bag from pieces of foliage, bits of bark, or other plant parts. The larva spends its entire life in this bag, and the female moth will be mated within this bag, where she also produces eggs. The eggs overwinter inside the bag.
Many adults look like wasps and fly during the day.
The immatures are referred to as borers and are generally found under the bark of the trunk and limbs. Remember, borers are opportunistic and are often better able to infest and survive in a stressed or weakened plant. By maintaining healthy vigorous plants, you can reduce your chances of major problems with borers. To illustrate the typical borer, I have used the dogwood borer as an example. The moth is dark blue, almost black, with yellow markings on the body.