Moved from Hackberry Psyllids. Under the assumption that this is indeed a psyllid gall, then based on the host, the location, the position of the gall on the plant, and the gall's overall appearance in accordance with Tuthill's brief description (apparently the only description?), then it must be this species. While many "undescribed" "species" of leaf-galling Pachypsylla forms exist, the same cannot be said of the stem- and twig-gallers, of which just a few species are known with relatively well-defined species boundaries. The other bud-galler, P. celtidisgemma, does not form pubescent galls (image); P. celtidisinteneris forms stem galls underneath the bark; the galls of the last species, P. dubia, are unknown, but the adult's affinity to P. celtidisgemma makes it probable that it has similar galls as well. That just leaves pallida, which has densely white pubescent bud galls.

This is apparently a very poorly-known species known from just a few collections. Yang & Mitter emphasized the uncertainty surrounding this species, postulating that the bud-gallers may comprise just a single species (1), though their study did not investigate this further, perhaps due to insufficient material and probably also due to their focus on the leaf-galling species. The adult, however, based on Patch's images, appears to be quite distinct from P. celtidisgemma. I would love to see adults reared from one of these someday.

Moved from Unidentified Galls.
Identified as a psyllid gall by Dr. Raymond J. Gagné.
[Added 12/30/2010] Dr. John Moser says "Pachypsylla pallida Patch 1912. - The hairy bud gall?" I can't find any descriptions of that gall, but I did find a reference to Celtis reticulata being a host for this psyllid.