Catkin gall [on Juglans hindsii]. The mites infest almost every male flower in the drooping catkins. There is considerable malformation with excessive development of individual flowers, each resembling a miniature cauliflower head. Galled catkins on a tree are conspicuous from the ground as a green or dirty brown, blackish, lumpy mass. They begin to deteriorate in July, becoming heavily infested by the mildew fungus. Infested catkins often remain attached to the tree so that galls can be seen throughout the season. The mites seem to have the effect of prolonging the life of the catkin. Although female flowers are heavily infested with mites, they do not show signs of malformation.

The male, protogyne, and deutogyne were found inhabiting galled male catkins and female flowers during June-July. The life cycle of this mite has not been observed. Eriophyes spermaphaga was recently discovered on catkins of Hind's walnut from California. No collection has been made in other areas. This species should not be confused with Eriophyes neobeevori Keifer, which causes similar injury to catkins in California walnut {Juglans californica S. Wats.) in southern California.