The Mystery of Falling Clay Balls: Yellowjackets Exposed

For weeks, tiny red-clay pellets rained onto decks and driveways in Hall County and Marietta. Theories ranged from meteor dust to artillery fungus. UGA entomologist Bob Matthews identified the source: yellowjackets.

Why Yellowjackets?

• Late June–September: nests expand exponentially, requiring massive excavation.
• After rain, digging frenzy: 7 of 10 wasps carry clay pellets away, dropping them yards from the nest.
• Look for a soccer-ball-sized underground nest within 50 ft; watch at dusk/dawn for shimmering flight paths.

Why Not Other Insects?

Cicada killers push soil out and re-enter; they don’t airlift pellets. Mud daubers drop few pellets right at the nest. Yellowjackets are social, cooperative excavators—hence the widespread “rain” of clay.

Can you help Bob study mud-dauber spider hunting? Email him.