The grubs dig deeper in winter and come back up toward the surface when it warms up. After a couple of years of living like this they can go berserk with a springtime population boom into the world above. Their adult selves begin to live up to their Greek names by eating copious amounts of leaves.
Just like the recent termite horde that visited Camp Salmen, the June Bugs are looking for love in mass quantities and soon the females will lay eggs for next year's batch. They have a deep fascination for outdoor lighting and buzz around any old light fixture after dark, even finding ways to blunder into people’s kitchens and land in their soup. You may have noticed one species (the metallic green ones) have the nutty behavior of cruising around on their backs like the Three Stooges. Since they only come out at night and hide by day it is supposed that exposure to too much light is bad for them, which may be why they leave their carcasses lying around everywhere.
They only just act stupid around humans; otherwise, they are absolutely harmless to them. However, by attacking turf roots when they are grubs they can make large, brown patches on pretty, ideal lawns. This severely disappoints those who are fastidious about their lawns and for this, these folks insist, the grubs must die.
This can be done with treatment by insecticides but for those philosophically against such measures and/or those who prefer imaginative or devious means, they can try counter-biologic warfare with the cunning application of Milky Spore bacteria or attack nematodes that can go toe to toe with the grubs in the grass. If you can figure out a way of encouraging them, there is a parasitic wasp that will go after the grub. Even hand picking works; lifting up the turf and grubbing around in the dirt, but one would have to be pretty intensely committed to go that far.
If it’s too late, they’ve already hatched and are now buzzing around your head — you’ve not lost the war. You could build a trap with a bright light over a bucket with some oil and water on the bottom. If that doesn’t suit your taste you can go the subtle route and start a little earlier in the season by encouraging snakes, bears, songbirds, chickens, armadillos, skunks, moles, lizards and geckos to roam on your property. These animals love June Bugs for food, will have a Feast Day in June and will be most appreciative.