Sacramento jumping "pollen grains"

When Michaelson and Ben were up here this summer they pointed out to me some yellow granular material on the blacktop parking lot surface which seemed to be moving. Random "grains" were hopping under the heat of the day. We couldn't see that it made any difference whether they were in full sun, partial shade, or full shade. But if we stared long enough at a patch of the stuff, we'd see some of the "grains" start jumping like popcorn. The boys, of course, asked me what it was and I had to admit I didn't know. But I had noticed the phenomenum in our own access driveway and asked a few people without success.

Then the other day an article appeared in the Sacramento Bee which explained it all.

I've noticed numerous minute, cream-colored "seeds" flopping up and down on the ground under an oak tree. They seem to be in clusters on the driveway. I sprayed them with wasp spray, and they seemed to go away. Do you have any idea what this might be?


Sounds like jumping galls, a very harmless and very important part of the oak ecosystem. They look like tiny yellow or brown seedlike objects that hop around.

The galls are caused by a tiny wasp. It lays its egg in an oak leaf, and it causes a malformation, sometimes very pretty ones, at that spot. The gall provides a home to the wasp larvae.

In summer, they fall to the ground with the wasp larvae inside. The larvae move around, and that causes the galls to move; hence the name "jumping galls." Some experts think the movement helps drive the galls into the duff or soil so they aren't easy targets for birds.They're actually fun to watch, and you have to admit it's an amazing adaptation of nature.

The galls and wasps are harmless to people. You've probably seen other galls: the big oak apple ones, as well as ones on leaves that look like pink star bursts or white chocolate chips.

A tip: Never spray insecticide willy-nilly. Know your pest first, so you know you're destroying something harmful rather than something beneficial, and make sure the product you're spraying is approved for that use. In this case, harmless, beneficial insects were killed.

– Pat Rubin

Pretty good explanation.