Damage from May beetles often appears in the spring and early summer, before injury from other white grubs becomes evident. Another interesting kind of white grub is the green June beetle, Cotinus nitida. Daytime resting sites of green June beetle larvae can often be found near such sites and are marked by small mounds of soil on the lawn surface. The larvae have a curious habit of crawling on their backs across the soil surface to move from one site to another. Adults of the green June beetle are velvet green on the top, metallic green below, and are approximately 1 inch in length.
Adults fly during the day and feed on over-ripe fruit.
The May beetle, Phyllophaga congrua, requires two years to develop. For simplicity, the following discussion will be limited to species with one-year life cycles. Once a year, in late spring or summer, adult beetles emerge from the soil to mate. Mated females then return to the soil to lay eggs. Within about two weeks the eggs hatch into small white grubs that feed on grass roots.