Borer or carpenter bees are large bees that create nests by tunneling into wood. They're usually solitary or live in simple societies formed around related females. They're important pollinators for open-faced flowers but are considered pests when they burrow into wooden structures.
Borer bees resemble bumblebees, but they have shiny abdomens lacking the hairs seen on bumblebees. They seldom sting unless caught or otherwise provoked. They seldom cause major structural damage, as their tunnels are usually close to the surface. Borer bee holes are about 1/2 inch wide with yellow staining from the bees' feces. Plugging and filling the holes will usually kill any bees inside.