These incredibly bold blotches on a red maple leaf turned me into a sleuth - what were they? What had made them? They look like eyes staring at me!
Turns out it's from the Maple Eyespot Gall Midge, a mosquito-like fly that lays its eggs exclusively in red maple leaves. The larvae (maggots) feed on the leaf tissue, secreting a hormone-like substance that causes the pigment around each gall to change color.