Goldenrod Gall Fly larvae live inside the stems of goldenrod. The fly larvae manipulate goldenrod into creating spherical feeding sites for the fly larva. Larvae are protected against the wind and rain, and manipulate the plant into providing a continuous source of nutrition.
In summer, larvae are in a state of growth and development. They cannot withstand temperatures below freezing. In autumn, the larvae are fully developed and the plants senesce. About this time of year, the larvae acquire freeze tolerance.
During the cold winter, the sturdy stalks and many galls are visible above the snowpack. The gall provides little shelter against the cold. Larvae can resist freezing at 0 Centigrade and do not begin to freeze until temperatures drop below -8 C. Up to 60% of the water inside a larva can freeze without killing the larva. Larvae have survived temperatures as low as -55 C. In the heat of late summer, larvae are already prepared for the cold weather to follow.