Can these critters be trapped?
Following is an excerpt from an eXtension publication that discusses yellowjacket traps. Most hardware stores and garden centers sell such traps.
"Various types of traps can be used for certain species of yellowjackets. These are typically baited with liquid or dry attractants and allow insects to enter but not escape. They may be useful for monitoring the types and relative numbers of these species present, and if used in larger numbers, may help to suppress populations. This strategy may be most useful where a problem is caused by insects nesting on an adjacent property you do not own. Competing food sources will reduce the effectiveness of traps. Trapping around a concession stand will reduce the numbers of yellowjackets at the concession stand. Traps should be placed out of reach of children when possible."
Go here to read the complete bulletin: IPM Action Plan for Yellowjackets
The following bulletin suggests reducing yellowjacket populations by monitoring and removing queens and nests in the spring: Yellowjacket Control — Now Is the Best Time to Do It