Insects and Spiders - native

California Prionus Beetle (Prionus californicus) on Aug 22, 2025

Originally reported as Ponderous Borer (Trichocnemis spiculatus)

Submitter does not have a specimen

Description of specimen

1.5-2 inches beetle with serrated antennae, furry brown thorax on bottom, smooth on top, Mahagony-brown oval smooth shiny (but not metallic). Not sure my ID work is correct. We have so many trees loose life here in our area before full maturity.

Commentary

Thank you for your report! This is actually California prionus (Prionus californica). The Ponderous borer is EVEN BIGGER. Both of these species are native beetles and neither are considered pests as they do not attack living trees. Their grubs live in conifer stumps and logs. There are other borers, mostly native, that will infest stressed and dying cedars. Summer droughts are very hard on the trees.

Tom Valente
Aug. 25, 2025, 1:49 a.m.

Location

Sitting on backyard facing porch, at 10 pm. Backyard is dead-ending at highway 205. Vegetable garden with about 10 fruit trees, and mixed very mature deciduous and evergreen trees, and grazing grass area for four sheep. Single family homes properties, 1-3 acres lots, zoned in 1960s...1970s... Prosperity Park Road.

Expert Reviewer

Tom Valente
Oregon Department of Agriculture

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