Andricus dimorphus

Confirmed hosts of the clustered midrib gall wasp are white oak species, including Quercus macrocarpa, Q. alba, Q. prinoides, and Q. bicolor.^[1][2] Clusters of up to 50 globular (but with a pointed base), red-brown galls are formed along the midrib on the underside of leaves beginning in late summer.^[1][2][3] The galls readily detach from the leaf, particularly when mature.^[1][2][3] Adults emerge from the galls the following year.^[2][3] Inquilines and parasitoids may inhabit the galls.^[4]

This species was first described by William Beutenmuller in 1913 with the name Cynips dimorphus.^[2] According to Clarence Gillette, William Ashmead had already used this name by 1889 for a species that produces galls similar to those of Beutenmuller's Cynips dimorphus.^[5] This species was later transferred to the genus Adleria which itself was subsequently included within Andricus.^[6]