The idea that flies only live for 24 hours is incorrect, though they don’t have long lives. Life expectancy varies by species, ranging from about a week to nearly a year. Flies spread disease rapidly because they land frequently—their wings can’t support their weight for long. Each time they land, they deposit bacteria that may cause serious illness.

In Arizona, house flies and drain flies are the most common. They breed quickly in warm, moist environments and often indicate sanitation issues. Indoors, even a small fly problem can grow fast if not addressed.