What are those red and white circles on the maple leaves? The bright, colorful circles really stand out against the green leaves. They look like little bullseyes.
These spots are a maple eyespot gall, caused by an ocellate gall midge (Acericecis ocellaris). The larvae develop in the leaves of maples in the spring. They use the nutrients in the leaves to grow. As they are eating, they release hormones that cause the leaf to change color and form a protective layer over them (the gall). After a few weeks, the larvae drop to the ground, dig a hole, and pupate. The adults come out of the ground in the following spring, lay eggs on the leaves, and start the process all over again.
Have you seen any maple eyespot galls this year?