Caterpillar Invasion Hits Menlo Park Area

Thousands of western tussock moth caterpillars swarming trees and public spaces

Apr. 15, 2026 at 7:40pm

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An abstract painting in earthy tones of green, brown, and ochre, featuring sweeping geometric arcs, concentric circular patterns, and precise botanical spirals, conceptually illustrating the complex life cycle and swarming behavior of western tussock moth caterpillars.A visual representation of the sudden population explosion of western tussock moth caterpillars in Menlo Park, capturing the intricate patterns and natural rhythms of this ecological phenomenon.Menlo Park Today

A population explosion of western tussock moth caterpillars has hit the Menlo Park area, with the fuzzy insects dropping from trees in droves near downtown Menlo Park and Flood Park. The caterpillars, which favor oak trees, have emerged earlier than usual due to an unusually warm March, creating a nuisance for residents and prompting the city to actively remove them from high-traffic areas.

Why it matters

The sudden influx of caterpillars is an unusual phenomenon that highlights the impact of climate change on local ecosystems. While the caterpillars are not dangerous, their presence can cause skin irritation and disrupt outdoor activities in the affected neighborhoods.

The details

The western tussock moth caterpillars typically appear during the spring and summer months, but the warm weather in March caused them to emerge all at once this year. The caterpillars are now dropping from trees in large numbers, creating a fuzzy carpet on the ground and prompting concerns from residents. The city of Menlo Park is actively removing the caterpillars from high-traffic areas like parks, playgrounds, and the downtown district.

  • The region experienced an unusually warm March, likely causing the caterpillars to emerge earlier than usual.
  • The caterpillars are typically seen during the spring and summer months.

The players

Kyle Risser

An entomologist who discussed the western tussock moth caterpillar invasion with local media.

Menlo Park

The city is actively removing the caterpillars from high-traffic areas like parks, playgrounds, and the downtown district.

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What they’re saying

“A fuzzy invasion is taking place on the Peninsula.”

— Raj Mathai, NBC Bay Area Anchor

What’s next

The city of Menlo Park will continue to monitor the caterpillar population and remove them from public spaces as needed to mitigate the impact on residents and visitors.

The takeaway

The sudden influx of western tussock moth caterpillars in Menlo Park is a stark reminder of the ways in which climate change can disrupt local ecosystems. While the caterpillars themselves are not dangerous, their presence highlights the need for ongoing monitoring and adaptation strategies to address the effects of a warming climate.