The 2.5 to 5.7 cm adults, which are reddish-brown with smooth shiny
wing-cases, emerge from the soil from June to early August. The males are smaller than the females and have more strongly serrated
antennae. The adults do not feed. They fly at night, seeking mates. Males appear to be more active, while females produce a
pheromone to attract males. The female-produced sex pheromone compound has been identified as an isomer of 3,5-dimethyldodecanoic acid. A synthetic mixture of all four possible isomers of 3,5-dimethyldodecanoic acid is highly attractive to male
P. californicus in field trials. The life span of the adult
P. californicus is 10 – 20 days. Shortly after mating the female lays cream to yellow-brown 4.8 mm long eggs, of which she can produce up to 200 in her lifetime. She lays them 1.25 to 3.8 cm below the soil surface near the roots of suitable hosts. The
larvae, cream to brown in color and strongly segmented, seek out roots shortly after hatching. They furrow and tunnel through the roots as they consume tissue, moving upward and inward and often killing apical regions. Age distribution data suggests that larvae move from smaller to larger diameter roots as they age and grow from 6.5 mm to 7.6 cm, eventually reaching the root crown.
Pupation occurs near the soil surface in a cell constructed of soil and root material. The 2.5 to 5 cm cream pupa look like the adults. ==Economic significance==