Those are gaint green june bugs or Cotinous beetles. They are the big grubs found in your mulch or grass. As grubs tbey will move on their backs not using their legs. I would put down some grub b gone or any granular insect control. The grubs feed in the roots of your grasses and plants. The grubs are foood for the moles, who makes your grass fell spongey. Then you have lazy yelliw jackets who.take over holes of the moles for their nests. So get some grub granular to put down on your grass area and garden beds. I out down the granular on the mjor summer holidays, memorial day, 4th and labor day. I hope this helps, even tbough its a long answer.