Galling!

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. 

They then drop to the ground, where they pupate and emerge as adults the following spring, to fly around, mate and lay more eggs. It spends a lot of its life in the ground, metamorphosing.

I love investigating!