May 21, 2020
Pop quiz: What does the goldenrod gall fly (Eurosta solidaginis) have in common with your car? The answer: They both contain antifreeze! (Also, I guess they both have at least one antenna.)
These small flies can be found across the U.S., generally in the vicinity of goldenrod plants. They lay their eggs near the new buds of a goldenrod, and when the eggs hatch, the larvae crawl below the bud and induce the plant to form a gall (a hard chamber made of plant tissue) around themselves. They stay inside the gall until they emerge in the spring as adults.
However, the gall doesn't offer much in the way of insulation for the soft-bodied larvae, and they sometimes have to endure long, hard winters. Just how they accomplish that has been the subject of a great deal of research. It seems that once temperatures start dropping, the fly larvae begin producing glycerol and sorbitol. Both of these compounds serve as a kind of antifreeze and lower the melting point of the larvae's body fluids, which prevents them from freezing solid (Fun fact: glycerol was once used as an automotive antifreeze until it was replaced by ethylene glycol, and while it's not quite as effective as ethylene glycol, it's non-toxic).
Goldenrod gall fly larvae also serve as an important food source for a number of birds, such as the black-capped chickadee and the downy woodpecker. When food becomes scarce in the winter, these birds will often break open goldenrod galls and eat the tasty larvae within.
Thank you to VMNH Executive Director Dr. Joe Keiper for identifying this guy for me! #BenInNature
About this post: Social distancing can be difficult, but the next few weeks present a great opportunity to become reacquainted with nature. While he is working from home, Administrator of Science Ben Williams is venturing outdoors each day to record a snapshot of the unique sights that can be found in the natural world.
This post brought to you by VMNH Corporate Supporter Janet and Richard Ashby.
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