Richard Wiseman who wrote the history of the flea circus article available on Walt Noon's site has brought out a book called Quickology.
"‘Quirkology’ is a term coined by Prof Richard Wiseman to refer to psychological research that is quirky. Much of this work uses mainstream methods to investigate unusual topics, or unusual methods to investigate mainstream topics."
In the flea circus article Richard Wiseman also mentions "Nightmare Alley" a novel by William Lindsay Gresham. If you have a copy of this book and know of the flea connection there then please let me know.