confluenta or quercusspongifica

A. quercusspongifica has sometimes been referred to as A. spongifica.

A. confluenta has sometimes been referred to as A. confluens.

Galls of both species appear with the leaves in spring.

Galls placed in this section could be caused by either Amphibolips confluenta (Harris, 1841) or A. quercusspongifica (Osten Sacken, 1862). Felt (1) describes the former as follows: "Globular, smooth, shining or opaque leaf gall, internally a juicy, white, spongy substance and a large central, larval cell, green, turning with age to light brown, diameter 1 1/4 to 2 inches, usually on a vein or petiole, on scarlet, Spanish and black oaks, in May and June." He does not include A. quercusspongifica, whose galls Weld (2) describes only as "similar in size and appearance to the above." Weld lists Quercus coccinea, rubra, falcata, marilandica, and texana as hosts for A. confluenta, and Q. coccinea, rubra, falcata, velutina, ilicifolia, and palustris as hosts for A. quercusspongifica.

Weld does note distinctly different phenologies for the two species: Adults of A. quercusspongifica have all emerged from their galls by the end of June [in Chicago, DC, Connecticut, and Ontario], whereas galls of A. confluenta in Ithaca, NY still contained pupae on August 1 and adults on September 12, and in Connecticut and Toronto adults were recorded as emerging from galls in November.

Neither of these references illustrates A. quercusspongifica, and all illustrations of A. confluenta galls show them as perfectly smooth, without the conspicuous bumps present in some of the BugGuide images. What this means exactly is unclear; there don't seem to be any other northeastern species that could be responsible for these galls.