ocellate gall midge

red maple (Acer rubrum var. rubrum)

The larva produces a flat, 5 ⁄16″ to ⅜″ in diameter gall on the upper surface of a red maple leaf. The gall is a yellow or greenish-yellow “eyespot” bordered by a ring with a red inner edge and a purple outer edge. The center of the spot is slightly raised and may be green, yellow, red, or purple. The larva is unprotected in the depressed center of the spot on the underside of the leaf.

Septoria Leaf Spot (Septoria aceris) is a fungus that produces dark brown or tan spots with light brown centers. Black fungal bodies are visible on the upperside of the leaf under magnification.

The larva feeds on the leaf at the center of the spot on the underside of the leaf.

The female deposits eggs singly on the underside of red maple leaves. After the larva hatches it feeds on the leaf and injects a hormone which causes the leaf to produce a gall. It spends 8 to 10 days on the leaf, growing to a size of about 1 ⁄16″ in length. It then drops off and burrows into the ground. It overwinters in the ground as a pupa and emerges as an adult early May the following year.

Sources: 7, 29.

Larva

Gall

Leaf