A grass grub beetle caught in the web of a garden orb web spider. The beetle was already dead and spinning in the breeze. Grass grubs are native to New Zealand. They used to fill a modest niche, feeding on the roots of native grasses. Then the farmers came, covering the country with many varieties of pasture grasses. The grass grub population exploded, making it a major threat to farming. The grubs eat grass roots and the adult beetles eat the leaves of trees and other plants.