Contarinia negundinis

Aceria near-campestricola

Eriophyes u-thomasii-frost-gall

Cecidomyia negundinis

Acer negundo

Swellings on the midrib of the leaflets of the Box Elder, much resembling Cecidomyia pellex on the White Ash. The swellings form two long circular chambers, one on either side of the midrib, opening on the upper surface by slits running the whole length of the gall. Occurs on Box Elder  (Acer negundo). Not common.

Eriophyes ulmi

The galls are intermediate in form between those of the hard and soft maples [ie, Vasates aceriscrumena and Vasates quadripedes] and somewhat balloon-shaped. The interior wall is ridged vertically. The galls usually occur on the upper side of the leaves. Occurs on soft elm (Ulmus americana) and Rock Elm (Ulmus racemosa [thomasii]). Very common.

Eriophyes sp. 

It differs from the frost mites on Hard Maple and Beech, in that it does not consist of a mass of spherical granules, but of a mass of tangled threads which under the lens are seen to be arranged in very beautiful star-like clusters. The mites are easily found among these. The patches are found on the under side of the leaves betwen the ribs. Occurs on Rock Elm (Ulmus Tacemosa). Common 

Insect Galls of Ontario