The North American gall midges (Diptera: Cecidomyiidae) of hackberries (Cannabaceae: Celtis spp.).
Twenty-three species of gall midges occur exclusively on hackberries in North America north of Mexico. Twenty-one of them belong to the genus Celticecis and form complex, dehiscent galls on leaves and the current year's twigs. Celticecis species are definitely known only from the typical subgenus of Celtis, distributed through much of the Holarctic Region. Nearctic species do not appear to discriminate among hosts within the subgenus but each its individual geographic limits. Galls of most species of Celticecis grow quickly in early spring, but some have a delayed, late summer development.