Megan's Nature Nook
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Going on a walk through the prairie you’ll most likely come across one of these, which are easiest to spot once the leaves and grasses start to die down. You may have stopped to look and wondered: gall, what is this? Well, it’s an insect home! This gall is formed during the Goldenrod Gall Fly’s life cycle. Here’s a quick rundown of all that happens inside that little gall: Female Goldenrod Gall Flies lay an egg on the tip of an emerging Goldenrod in the spring. When the egg hatches, the larva burrows its way down to the inside of the stem. The action of chewing and saliva from the larva stimulates the plant to produce more growth hormones, and as a result the gall starts to form. This gall will then provide food and shelter for the growing larva throughout the summer, fall, and winter until it is ready to emerge in the spring. In fall, as temperature decrease, the larva will produce a glycerol, an anti-freeze. This allows a majority of the body tissue to freeze, but keeps the cells from freezing - even on chilly days like today! They spend the winter as little larva popsicles, just hanging out and waiting for spring to arrive. Something else they do in the fall in preparation for their escape from the gall in the spring is to dig an exit tunnel right up to the outer layer of “skin” on the gall. They leave this outer layer so that they will still have protection from the elements throughout the winter. Once spring finally rolls around, the warmer temperatures signal the larva to go into a pupa stage, and then finally transform into the adult fly. This is where things get interesting. In order to get out of the gall, the fly must break through the outer skin of the gall. The fly anchors itself at the end of the exit tunnel, then pumps a special part of its head full of body fluids, inflating it like a balloon. The “balloon” causes the outer skin of the gall to break open and then the fly can pull itself out. The fly will rest and give time for its wings to inflate and dry. Then it is off to find a mate and start the process over again. The adult flies live for only about two weeks and don't eat during that time. They are not very good fliers, and mostly walk as their mode of transportation. Who knew so much was going on inside of that little gall? This was even the condensed version! If you would like to learn more in depth about the galls, and the life cycle of a Goldenrod Gall Fly, take a look at this article, Bug-sicles in the Class Room: Demonstrating freeze tolerance with larvae of the Goldenrod Gall Fly! by Doug Collicutt. He even talks about an interesting little freezing and thawing experiment you can try with Gall Fly larva! The gall is a pretty safe place for the larva to hang out for almost a year of its life, but there are some dangers they can still endure. Some insects, like wasps, will lay their eggs in the gall and the wasp larva will eat the gall fly larva. There is a beetle that will burrow in the gall for a tasty treat. Black-capped Chickadees, Downy Woodpeckers, and some other small birds can peck into the gall to get a tasty little snack. I have also heard that the larva can be used for ice fishing bait, but I have yet to test that theory myself. Maybe they would be a good protein packed snack for humans, too..?!! You can try it and let me know how that goes! Next time you’re out for a hike in the prairie, keep your eyes open for galls. Check to see if any of them have been pecked at by birds, or if they’re still safely awaiting the arrival of spring. Goldenrod Gall Fly Galls are not the only galls out there. There are different kinds of galls that can look very different in size and shape because they are created by different species. Not only are they on Goldenrod plants, but they can be found on other plants too, including trees! Who knew that something so small could have something so complex going on inside of it? Little natural wonders like galls often get overlooked. So, go out and enjoy the Great Outdoors! See what you can discover!
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