Japanese Beetles

Japanese beetles are about 1.5-2cm long, green coloured with bronze wings. 

Japanese Beetle Adult-photo Iowa State University

Description 
They have small patches of white hairs on their bodies. Grubs are white to cream and the typical c-shape. They measure about 2.5 cm long when mature.

Eggs, larvae & pupae-photos USDA Animal Plant Inspection Service

Habitat and Lifecycle
They are found in most of the USA, parts of Canada and many other countries in the world. Japanese beetles are not native to the USA or Canada. They overwinter in the soil as larvae and in spring begin feeding on grass roots. Once they emerge the adults are voracious! Adults mate in the summer and the female lays 40-60 eggs in the soil. June and July are the peak months for these predators. There is only one generation per year. In colder climates their lifecycle may take two years.

Damage-photo University of Kentucky

Diet and Damage
They attack roses, ornamentals, most trees and shrubs, many veggies and grasses. They will attack almost anything and it is reported they prefer at least 300 different species of plants. These guys can cause serious problems to the home gardener. They chew holes in leaves and flowers causing the leaves to look skeletonized. Eventually affected plants will die.

Control
1) Hand Pick
When you find them destroy them & their larvae. Best time to do this is in the morning before they are fully active. The little hand vacuum is a handy tool for handpicking as well.
2) Beneficials
Birds, wheel bugs, parasitic wasps, robber flies and praying mantids. Skunks, moles and shrew eat grubs.
3) Milky Spore Disease
You can buy this at any nursery and it will kill the grubs. Apply on your lawn in the spring and then again after the adults begin to die off at the end of the summer.
4) Row Covers
Use row covers when the beetles are in flight.
5) Sticky Traps
Make some sticky traps with tanglefoot, collect the beetles every morning and drop in hot soapy water.