Green and blue bottle flies indicate

• A. Open drain
• B. Clogged drain
• C. Leaking sewer line
• D. Dead animals

Answer: (D)

Green and blue bottle flies are drawn to decaying animal tissue. When you see them, it almost always points to a dead animal somewhere nearby—often hidden in a wall void, attic, crawlspace, or under the building. They lay eggs on carrion and their larvae feed on it, so their presence signals a concealed carcass rather than a plumbing issue. Drain-related problems tend to attract different flies, like drain flies, which look and behave differently. So the best fit is that there’s a dead animal source somewhere, which is what you’d investigate and address.