Tooele Transcript Bulletin – News in Tooele, Utah

February 25, 2016
Prionus californicus larvae are more destructive than adults

When you see the prionus californicus’ appearance as an adult, many immediately assume that the damaging results of this beetle would occur during its adulthood. However, the only harm an adult prionus californicus is capable of inflicting is a painful bite — usually administered when disturbed.

The real devastation is caused by the larvae. During its 3-5 years of progressive growth, the prionus californicus’ larvae burrow in the ground to feed on the roots of plants and trees. Many inflicted plants include oak, poplar, black walnut, conifers, fruit trees, grape vines, hops, brambles and cane berries. Most of the trees and shrubs that become infested suffer a yellowing of leaves and even death.

After prionus californicus beetles outgrow their larvae stage, they immediately seek out mates to reproduce, as their adult lifespan only lasts up to 15 days. Males, during the nighttime, will locate a female by tracking her emitted pheromones. Once she mates, she will lay her eggs underneath the soil of a provided host tree. There, the eggs will hatch, eat, grow, and restart the cycle.

Adult prionus californicus beetles grow up to 2 1/2 inches long. They are a sleek reddish-brown color and possess long saw-like antennas. Adults are nocturnal and are attracted to light. In Utah, adults begin to emerge from the soil in July and August. This beetle does not normally appear in desert areas, but does distribute in North America from Alaska to Mexico. The prionus californicus beetle never eats as an adult — its entire focus is spent finding a mate. Not only are these beetles equipped with large mandibles intended for biting pesterers, but they also have wings. So watch out, they fly and bite!

Taylor Lindsay is a writer and photographer of wildlife creatures big and small. She can be contacted at

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