I'm probably not alone in these galls being one of the earliest, if not the first, to open my eyes to the wide world of plant galls. Nevertheless, mine is a cautionary tale. I did not know that maple bladdergalls are a gateway-gall; they can lead to a serious hard-core gall-addiction. Before you know it, you're standing before groups of people saying, "Hello, my name is [your name here], and I'm a gall-oholic."
My gall-habit stemmed from learning the fascinating story behind plant gall formation; read on at your own risk! Eriophyid mites direct gall-growth by inducing plant genes to activate and deactivate at just the right time to cause newly differentiating leaf cells to form the same plant structure; the tiny cigar-shaped mites live inside the bladdergalls. Vasates quadripedes never produces any other type of gall. The equally common maple spindle galls are produced by a different eriophyid mite, V. aceriscrumena; this species never produces bladdergalls.