Twig Galls are Rupturing, 10-13-19

Up at 7:00 am today, and I headed out to the American River Bend Park for a walk. It was a chilly 43º at the river in the morning and got up to 80º by the afternoon. I’m really liking this fall weather. It’s one of my favorite times of the year. It was still smelling smoky outside, but not as bad as it was yesterday.

I took a different route than I normally do for my walk, hoping to maybe see something a little different, but the “between the seasons” lack of subject matter continued. I did get to see two different species of wrens: the Bewick’s Wren and House Wren. Those little, buzzy guys are staking out territories this time of year.

An easy way to tell the Bewick’s Wren, Thryomanes bewickii, from a House Wren is to look for the bright white eyebrow over the eye. The House Wren doesn’t have that.

The standout for the day, though, was actually the galls of the Ruptured Twig Gall Wasp, Callirhytis perdens. They are “rupturing” this time of year. The tiny wasp lays its eggs inside the softer twigs of the Live Oak trees, and the tree forms a capsule around each one. Then as the wasp larvae grow and develop, the capsules get larger and twig swells. When the wasps are ready to hatch out, the capsules burst out through the skin of the twig and fall to the ground, where the wasps escape their capsules and fly off. I think it’s odd for an insect to wait until October to go through its breeding cycle, but I guess there’s an insect for every season…

Galls of the Live Oak Gall Wasp, 1st Generation, Callirhytis quercuspomiformis

I also found a few first-generation galls of the Live Oak Gall Wasp (round balls with spikes on them), including a grouping of the galls. I’ve seen them singly before lots of times, but had never seen a grouping before, so that was cool.

CLICK HERE for the album of photos.

I walked for about 2½ hours and then headed back home.