"The bung is honey-colored at first, but whitens with exposure to weathering....The outer surface of the finished bung is flush with [a ring of raised plant tissue]."
"Light bung coloration is a galler rather than a foodplant trait, as shown by..."
"Ramets with light-bunged galls from Maryland, Michigan, and Ohio were identified as S. canadensis and S. altissima. The galler exhibits high fidelity to this foodplant complex as shown by..."
[goes on to emphasize the rarity of occurrences of light-bunged (therefore, made by this particular Gnorimoschema species) galls on S. gigantea, S. ulmifolia, "S. juncea-missouriensis complex" [almost certainly S. juncea at this eastern site]]
[Miller mentions that "S. nemoralis" was given as the host by Riley in 1869, but emphasizes that he has personally never found Gnorimoschema galls on this host species, despite searching, and also casts doubt on the identity of the gall-former responsible for galls Riley reported from S. missouriensis from Washington and British Columbia.]
”- William E. Miller: (2000) A Comparative Taxonomic-Natural History Study of Eight Nearctic Species of Gnorimoschema that Induce Stem Galls on Asteraceae, Including Descriptions of Three New Species (Lepidoptera: Gelechiidae)©