Around the Island

Mashomack Musings: Winter’s gold in the meadows

While some animals leave Shelter Island for warmer weather during the winter months, many have adapted to survive the cold.

One of these winter survivors is the goldenrod gall fly. This parasitic fly uses the native goldenrod plant to ensure its offspring’s survival in the freezing temperatures.

How does this small fly do it? By selecting a plant to help with most of the work.

When new goldenrod plants begin to grow and bud in the spring, the female fly will choose a plant on which to lay her eggs. Just a hatchling herself, she has only 10-14 days to live and complete this task.

Once safely deposited on the plant, the eggs begin to mature into larvae and start eating their way into the stem of the plant, secreting chemicals as they go.

In response, the plant’s defense system begins forming a hard, spherical chamber around the larvae; that chamber is known as a gall. While rigid on the outside, the gall’s inside remains soft and acts as a built-in food source.

Even though the goldenrod plant will then boast a bulbous growth in its stem, the plant itself is not harmed and can continue to grow while allowing life inside to stay safe from winter’s freezing cold.

Inside their hardened home, the larvae remain dormant for months on end until warmer temperatures trigger their hatching in late spring. In mid-May, these flies begin their adult lifespan, continuing and beginning the cycle once more. 

With just under two weeks to live as an adult fly, and the rest of the year spent in various life stages within another host, the goldenrod gall fly is a true over-winter survivor.

Meadows and grasslands like those at Mashomack, where the goldenrod blooms, are some of the world’s most threatened — and overlooked — natural areas.

Our work to restore these spaces on Shelter Island provides needed habitat for a community of important native plants and wildlife species that are now threatened by climate change, such as American goldfinches, woodcocks, monarch butterflies, bats and bumblebees.

Next time you’re visiting the Preserve and find yourself in our meadows, look and see if you can find some of these galls and other signs of dormant life, all waiting for their time in the sun.

Mashomack Preserve is owned and operated by The Nature Conservancy, a global environmental nonprofit working to create a world where people and nature thrive. Our mission is to conserve the lands and waters on which all life depends. To learn more, visit nature.org.