Other Common Names
Goldenrod Gall Moth, Goldenrod Gallmaker
Synonyms and other taxonomic changes
Originally described as Gelechia gallaesolidaginis by Riley in 1869.
Explanation of Names
From Latin gallae- "of gall(s)" + solidaginis- "of Goldenrod"
This species is found in galls on the stems of Goldenrod (Solidago)
Food
The larvae feed on two species of Goldenrod: Solidago altissima and Solidago gigantea
Life Cycle
The female lays her eggs in dead leaves on, or in the leaf litter around, the goldenrods, where they stay dormant through the winter. The larva hatches in the spring, seeks out a plant, and burrows into the stem. Its presence causes the goldenrod to form a tumor-like structure called a gall, which encloses the larva and provides food for it. During the summer the larva pupates inside the gall, emerging in early fall to mate and lay eggs.
Pupa inside a gall
Remarks
Recent genetic studies seem to show that populations that feed on one species are different from those that feed on the other- even though there's no other way to tell them apart. This could eventually lead to the formation of two different species.
Another study is looking at how the caterpillars cause the galls to form, in hopes of learning how humans can modify plant growth.
Hymenopterous parasites include Chalcidoidea, Ichneumonidae and Braconidae.
See Also
Goldenrod Spherical Gall Fly A fly that makes a similar gall on the same host:

Internet References
ECOLOGICAL RELATIONSHIPS AMONG GOLDENROD PLANT AND GALL INSECTS Winter Science Curriculum Project at State University of New York, Oswego
Functional Genomics of the Solidago insect gall system Description of work on the biochemistry of interactions between gall insects and the goldenrod by Joe Miller of the University of Iowa. Has illustrations of the hostplant, galls and adults.