The goldenrod gall fly (Eurosta solidaginis) is a common and widely distributed insect of the central part of North America. Their entire lifespan is only two weeks, so mating begins soon after emergence from the gall. The newly hatched larva burrows into the stem of the goldenrod and creates the bulb-like gall which allows it to over-winter until hatching the following year. They can be harvested in the winter for a great ice fishing bait, but there is only one larva per gall.
"It takes a long time to grow an old friend." ~John Leonard