Wasps

I've been having a problem with wasps for the past several weeks — I suspect they've made a nest in a crawlspace under the house, and they've been coming up into the house through the bathroom downstairs (though I'm not sure just where). They're often weak and lethargic, so they don't seem to be much of a threat. I just caught a half-dozen of them and put them outside — they may be lethargic, but they're not always easy to catch — though most I find only after they've died, often on the windowsill.