Answer: What you describe sound like June Beetles to me. The adults fly at dusk, feeding on plants, mating and also depositing their eggs. They have a short lifespan but the eggs they lay turn into larvae which feed on grass roots. These are called grubs and when your lawn has a large population of grubs, you'll begin to see damage in the form of dead spots. Grub control products are readily available in the garden section of your local Home Depot. Be sure to apply according to label directions; timing is important and timing is different in different parts of the country.
Best wishes with your lawn!
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