Prionus californicus

The California Prionus is a giant long-horned beetle that spends the majority of its life underground, feeding on the roots of deciduous trees as larvae. When they emerge as adults, they live 10-20 days. Males seek out females at night, who remain in one spot emitting pheromones. As beetles they don't eat, and die shortly after mating and laying eggs. For the past few nights, there's been a lone Prionus sitting on the porch of the bathroom building, intimidating passers by with its large size (it's almost 4 inches long) and chunky mouth chompers. Given that they don't eat as adults, I wonder what the purpose of such hefty jaws is?

This species is actually a serious agricultural pest in the west--fruit trees may sometimes die from the larvae's thorough burrowing of the roots.