Blow flies are about 1/4 – 1” long with hair-like bristles and vary in color. Blow flies are often shiny, metallic, blue, green or black. They have large compound eyes, one set of wings and short antennae.Blow flies are attracted to recently deceased animals as well as animal feces where they lay their eggs. The grub-like larvae (maggots) infest the animal carcass for 5 – 10 days before they leave in search of a dry place to pupate. Blow fly larvae are beneficial in nature as decomposers of dead animal carcasses. The appearance of blow flies inside the home could indicate an animal has died within the walls, crawlspace or in the attic.