Goldenrod and Gall Fly Research
The goldenrod (Solidago Canadensis) is a native plant found throughout most of North America and parts of Central America. One interesting characteristic of the goldenrod plant is its ability to form a hollow pod, or gall, around its stem. The first time I saw the gall, I assumed it held inside it seeds for reproduction. My hypothesis was proved wrong however, as after I cut open the gall no seeds were present inside. Instead, a goldenrod gall fly (Eurosta Solidaginis) was perched within the gall. Adult gall flies typically only live for up to two weeks before they die. While they are still alive, the females mate and lay their eggs on top of goldenrod stems. After ten days, the egg hatches, and digs its way inside the plant stem. By chewing through the stem, the larva excretes saliva onto the plant creating a hormonal imbalance. The imbalance causes the plant to form a gall around the affected area. The gall offers both nutrients and protection to sustain the larva. The Larva slowly grows over the course of summer, and passes through several larva stages. One of the last things it does before winter is to dig a small tunnel to the edge of the plant wall within the gall. Over the winter, the larva manages to survive the freezing weather by using a body mechanism that acts like an anti-freeze. Once winter is over, the warmer temperatures cause the larva to turn into a pupa. The pupa stage lasts two weeks after which an adult gallfly emerges and crawls to the end of the tunnel. It inflates the upper part of its body until it bursts through the gall wall. It rests on the stem allowing its wings to dry before it starts the cycle over again. The interaction between a goldenrod plant and gallfly is an example of predatory symbiosis. The gallfly acts as a parasite invading the stem of the goldenrod plant and sustaining itself from it. The gallfly benefits from the interaction, but the goldenrod is negatively impacted....
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