Montana Field Guide

Recent genetic studies seem to show that populations of the Goldenrod Gall Moth, Gnorimoschema gallaesolidagnis , that feed on one species of Goldenrod (Solidago altissima or Solidago gigantea) 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.

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.

The larvae feed on two species of Goldenrod: Solidago altissima and Solidago gigantea.