The insects are Carrion Beetles in the genus Nicrophora. They're' most often found on or near carcasses. These beetles are scavengers; they won't damage people or pets.

So, I wonder if you trap mice, rats, or other critters in or near your greenhouse. If so, a search-and-destroy mission should resolve the situation. Once you find the carcass, use a plastic bag as a "glove." Next, insert your hand inside the bag, pickup the body, the pull the bag the bag off your hand and over the body. Secure with a twist tie, then discard in the trash.

By the way, all these insects in the images have wings. It's only obvious on the one which didn't tuck its membranous hindwings under the hard forewings.