Tuesday, October 12, 2010
Pine Cone Willow Gall
While out walking today, I chose an area in Moreau Lake State Park I'd never explored before, and I came across a willow shrub whose every branch was tipped with what looked like a grey-green pine cone. "Whoa!" I said, "willows don't have cones! Must be some kind of gall." When I got home I googled "willow galls" and right away found a match. This is a Pine Cone Willow Gall, caused by a gall midge, Rhobdophaga strobiloides.
As tiny as its name is long, this midge lays its eggs in the spring at the tips of willow branches. The eggs and their resultant larvae release a chemical that causes the willow leaves to form cone-like structures that encase the larvae and protect them over the winter. At some point, the larvae pupate, and adult midges emerge the following spring. Without mouthparts to chew its way out, the midge simply pushes aside the overlapping scales of the structure as it emerges. If some other insect hasn't parasitized it first, that is. This gall is apparently famous for harboring many other insects besides the midge that produced it in the first place.
I'd heard about galls like this but had never seen one. Surprises await everywhere.
I'm now awaiting an answer from BugGuide.net regarding the identity of this little beetle that looks like it was spattered with black paint. It was crawling on one of the half-eaten leaves of the gall-infested willow. I love its reddish legs and antennae that look like strings of tiny beads.