Yellowjackets are highly aggressive and often build nests in hidden locations such as underground burrows or inside walls. Because nests are concealed, activity may appear sudden or concentrated without an obvious source. Homeowners commonly notice yellowjackets flying in and out of a specific area, gathering around food, trash, or outdoor spaces. As the colony grows, activity becomes more frequent and more aggressive. 

Unlike many other wasps, yellowjackets are strongly attracted to human food, which increases the likelihood of encounters—especially in outdoor dining areas or near garbage. They can sting multiple times and will defend their nest if disturbed. Many stings occur accidentally, such as stepping near a ground nest or getting too close to an entry point. 

Because colonies expand rapidly, what starts as occasional sightings can quickly turn into frequent encounters and increased risk. Without treatment, activity will continue to grow throughout the season.