About six years ago while hiking the trails at the Highland Center for Natural History in Prescott AZ,  I noticed something that had been there all along but had escaped my attention on all my previous outings. It was a small round red ball on a scrub oak leaf about three quarters of an inch in diameter. It looked like a tiny red apple. As I examined this curiosity, I noticed there were others just like it on the scrub oaks all around me. What was I looking at? At first it appeared to be a fruit but it felt hollow and most oddly was attached to the leaf and not at the bud, in fact it appeared to have emerged right out of the middle of the leaf! Strange indeed. I then thought it must be an insect’s nest of some kind. Even more curious now I went back to the Center’s office and when I inquired, I was told it was a gall. What is a gall? Little did I know at that time I would be spending many hours over the next six years delving deeply into this question.

Charlie DeMarco is the founder of the Pinecrest Gall Research Station in Prescott.