Actually, I have some wasp killer to put down, otherwise I won't be able to mow the lawn tomorrow evening (don't ask, I hate wasps. If it wasn't semi-rational it'd be a phobia).
I heard it is true, but I've also heard it is false. I have not studied the phenomena myself to know for sure. I would offer to find out, but they'll hopefully all be dead (or dying) by tomorrow
don't think it's true of wasps, but it's certainly true of cockroaches - if you kill a cockroach by squashing it or whatever, it emits pheremones that make all the other cockroaches start breeding