There's a charm to try, Frank, that I found in my great-grandmother's household charm book: Aphaniptera Revelio. I gather it was more commonly known when fleas were generally more of a problem than they are today. Say the charm with a figure-8 wand motion over the area you want to check. The main point of the charm is to detect fleas themselves--if they're there, the charm will make a pinpoint burst of bright red light. BUT according to the charm book, there's a secondary application: it also detects any flea bites. The site of a bite will pulse with a pinpoint of red light for ten seconds.

I had Arthur try it, and he found nothing. So that's good news for us.