24
Mar
06

Goldenrod_Gall


 

Goldenrod_Gall

Originally uploaded by Camp Naturalist.

Goldenrod Gall

Here’s a gall on a goldenrod stem. This gall is created by an insect that causes the plant to form a home for the larva.  This gall is likely formed by a fruit fly called the goldenrod gall fly.  John Eastman in his very interesting book “The Book of Field and Roadside” states, “Just how this larva induces the chemical reaction that produces a gall remains one of nature’s elusive secrets – perhaps the larval saliva mimics plant growth hormones.” The larva eats a tunnel just to the edge of the gall leaving a thin tunnel cover in place.  Staying in the gall all winter the insect’s body actually freezes.  In the spring, the larva thaws and goes to the end of it’s tunnel, anchors itself and pumbs body fluid into a special portion of it’s head which bursts the tunnel cover open. 

Gall Raid 

Downy woodpeckers and black capped chickadees love to peck their way in and get a treat.  The conical hole in the gall above(see photo) is from a downy woodpecker.  Chickadees don’t leave a clean hole but shred the gall to get the larva.  Some humans also raid goldrenrod galls to use the larva for ice fishing.

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