What's with all the hornets/yellow jackets?

Up until this summer, I think my four boys have had a grand total of 2 bee stings between them. Since we've moved into this home, they've had 7 (I think). After some questions, I did discover that construction tends to drive them away from old haunts, so they go looking. Of course, what do you think is going on within 100 yards of our home - a complete new subdivision... which the boys have thoroughly enjoyed watching, with all the heavy earth movers and such, but that's another issue. Anyway, so I've used up almost two full cans of bee killer (that foam stuff that can shoot 20-30 feet is amazing). Thankfully, the nests are rarely bigger than 5-10 bees, but it only takes 1 angry one to cause a problem. Anyway, I've taken out five nests, and my mom (who was watching the boys while we were in Minnesota) took out one, too. That's two on the porch roof, two on the second story overhang, and two in the swing set (which contributed five of the stings in the last week). I took out the second story ones tonight, and just about got stung myself. The wind had picked up, and the spray wasn't quite as accurate as I would have liked. Those things are quick, but I've got a great trigger finger... and a strong sense of survival. Hmmm... how fast could I have gotten down that ladder while screaming and trying to swat off hornets. Thankfully, within the next few weeks we'll be gone. Do they have hornets in Lolo? ;)