Nature Nut: It's the time of year for galls

Although we are usually most interested in birds or larger animals, one small critter that has intrigued me for years and is not so visible, is the goldenrod gall fly. Less than half the size of our common housefly, this little insect is not often seen, but makes its presence known in the little round houses it lives in on goldenrod plants.

It is in these hard bulges in the goldenrod stem that the fly develops from an egg, to a wormy larva, to a rice grain-like cocoon before changing into an adult. The larva stage which looks like a little white, round worm grows inside the gall, essentially feeding on the inside of its house. Actually the plant grows the house around the egg as a chemical reaction to it.

This would seem like a safe place for the little worm to eat and grow before changing into a cocoon that will emerge as an adult fly next spring. However, there are a few predators that have figured out a tender morsel awaits them inside the gall.

Some of the best at this are the black capped chickadees and downy woodpeckers that make many a tasty meal during winter when food sources are scarce. By clinging to the goldenrod stem and tapping a small hole in the gall, these resident winter birds are able to penetrate the gall up to a half inch to get their meal.

Another ‘predator’ that has found the goldenrod gall larva a good food source is the hardy ice fisherman who harvests a bag of them off goldenrod stems before heading to rivers, lakes or ponds. Cutting the gall open with a pocket knife or Leatherman, they put the tiny worms on small hooks to entice slow but hungry sunnies and crappies.


Goldenrod galls are just one of hundreds of types of galls that can be found on plants just about everywhere there are woods and prairies. Around here some of the other more common ones include the oak apple gall, the willow cone gall, the cherry pouch gall, and the blackberry knot galls. Unlike the goldenrod gall caused by a fly, these are caused by mites or parasitic wasps.

A good time to see the galls is during winter when leaves have fallen and these growths are more obvious. So, if you need an excuse to get out for a hike this winter, just go out for a walk in the woods or prairies and look for galls. Once you find some, take pictures and look them up on the web if you are not sure who made them or what kind of plant they are on.

Or maybe take one home, put it in a jar and see if something eventually hatches. While such a hike may not sound exciting, it will give your heart a workout, make you smarter, and help pass the winter away. What more could you ask for?

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