Beetle larvae are often cast as the villains of the forest, as they can take down mighty trees with thousands of tiny nibbles. But this is the story of a longhorn beetle that’s a hero to our planet’s largest and oldest trees: It’s Phymatodes nitidus, or the Sequoia Cone Borer.
Sequoia pine cones continue to grow, remaining tight-fisted and attached to the stem, for decades. The trees release their seeds in three ways: By fire, by squirrel, or by beetle.
Fire is actually the preferred method: It heats the cones so they dry out, open up, and free the seeds to fall down to the ground, which is now devoid of scrub plants.
Douglas Squirrels eat cone scales and therefore free the seeds at their base.
Adult female P. nitidus lay eggs on the surface of pine cones, near where they attach to the tree. The subsequent larvae eat the scales of the cones from the central axis, helping to dry and open them, thus releasing the seeds.
I’ve seen these beetles a couple of times at Mount Pisgah, most recently just beyond the bridge on the Riverbank Trail. I’ve read that Sequoia Cone Borers use trees other than Sequoias as larval hosts, but I’ve not confirmed which trees. However, there is a stand of Coast Redwoods, or Sequoia sempervirens, near my most recent sighting.
Stay curious!
P.S. Don’t forget to check out Karen’s 2025 blog, The Daily Insect. Many of the featured creatures were photographed at Mount Pisgah.
Sources:
Relevant, and fascinating, chapter from a National Park Service 1975 study on Sequoia ecology: https://www.nps.gov/parkhistory/online_books/science/12/chap7.htm. Accessed 5/13/25.
University of California paper on Sequoia seed release: https://ucanr.edu/site/forest-research-and-outreach/giant-sequoia-sequoiadendron-giganteum. Accessed 5/13/25.
All photos by Karen Richards.