Aceria fraxini

[1][2] Range is North America, including southern Canada and most of the continental United States.

[3][4] The mites stay in the galls until late summer when host leaves mature.

[5]: 50 The life cycle is a form of alternation of generations.

An over-wintering generation consists only of females called deutogynes.

The other generation consists of both sexes: females called protogynes as well as males.