Tiny Jumping Beans

Jumping oak galls, Neuroterus saltatorius (photo by Donald Owen, California Department of Forestry and Fire Protection via bugwood.org)

24 July 2020

There’s a cool thing happening in California right now that we never see in Pennsylvania. In neighborhoods with white oaks there are tiny “jumping beans” in the gutters.

Here’s that they look like, recorded a week ago by Mary K Hanson.

They’re even better in slow motion, recorded by Mark Eagleton in Woodland, California.

Though they resemble the moths called “Mexican jumping beans” (Cydia deshalsiana) these galls are the agamic (asexual) second generation of tiny Neuroterus saltatorius wasps that mature on white oak leaves and fall to the ground.

Neuroterus saltatorius 2nd generation galls on back of oak leaf (photo by Steve Katovich via bugwood.org)

The larvae are tightly packed inside the galls so when they move the galls jump up to 3 cm. That’s 30 times the size of the gall!

In the fall the larvae become adult wasps inside the galls and overwinter to emerge next spring.

Neuroterus saltatorius are native to western North America from Texas to Washington state and up to Vancouver Island, Canada. That’s why we don’t see them in Pennsylvania.

Learn more at the University of Florida’s Department of Entomology: Neuroterus saltatorius.

(photos from Wikimedia Commons and bugwood.org; click on the captions to see the originals. videos embedded from YouTube)

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