Jumping Galls

August 17, 2011

I squatted down to look at what I thought were baby spiders jumping on the ground. Leaning in closer, I realized they didn’t have legs but instead appeared to be teeny seeds, a much smaller version of Mexican Jumping Beans. There were so many it sounded as if dew was drizzling all around me.

Afraid to touch them, I stood up and hollered at my husband, Joe, to come see. We squatted together, shoulder-to-shoulder, and watched dozens of them jumping in the perennial beds and on the slate steps where we hunkered down.

Joe touched a few and decided they were indeed seeds. I felt one with my index finger. It was as hard as a rock.

“I think it’s the heat that’s making them jump,” Joe said.

“It’s not that hot,” I replied as we both felt the slate step.”

I looked up into the oak tree above us. They couldn’t possibly be falling from the oak. Oak trees germinate from acorns, not seeds. But where are they coming from? Later that evening, sitting in front of my computer I typed in the only phrase I could think to Google:  Tiny jumping seeds. Surprisingly, there were several informational websites.

The seeds are actually Jumping Oak Galls also known as California Jumping Galls. Cynipid, non-stinging wasps (Neuroterus spp.) lay their eggs on the underside of leaves. Plant tissues develop, creating a protective gall around the lava. The jumping galls are only 1/25th of an inch in diameter, the head size of an old-fashioned straight pin. The larva moving within the gall causes the jumping.

California Jumping Galls usually drop by late summer to early fall and are considered harmless to trees. Metamorphosis changes the larva into a pupa which overwinters within the gall until spring. The emerging wasps are tiny, shiny black females, so small it’s unlikely anybody would see them. They lay eggs on oak shoots without male fertilization. The following generation is bisexual, winged males and females. Amazing! The reproductive cycle mysteriously continues. But who knows which generation of wasps will hatch in my garden, all females or bisexuals.

Nature never ceases to astound or entertain me. Teeny, jumping galls beneath the oak, making music that simulates drizzling dew, is one of many fascinating treasures. © 2011 Dianne Marie Andre


One comment

  1. Very interesting. I’ve never heard of them before. Thanks Dianne. bernadine


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