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House flies-here today, gone tomorrow

Q: I was wondering how long a house fly lives. -- Chelsi, Lehi, Utah

A: The house fly has one of the shortest life cycles known: a fleeting 20 to 30 days. Mating in the early summer, a few flies kick off a chain of events that produce millions of descendants by fall. In those few months, the original Adams and Eves will have launched ten generations. We humans would take 300 years to do the same.

[Jim Kalisch, U of Nebraska] In 30 days they're gone

Their typical life cycle flashes by like this: A female lays 100 to 150 white eggs--tiny things that look like long-grain rice. She lays 500 during her life. A half a day later if the weather's hot, the hundred or so eggs hatch into cream-white wiggly worm-like creatures called maggots.

About four days later, the maggots transform into brown pupae. The pupae stay quiet while the creatures inside work on their next change.

In another six days, the pupae begin to move slightly. Soon, the end of one cracks open and an adult fly squirms out. He flies away and his horde of brothers and sisters soon follow. Within a couple of days the adults find mates and start the next generation. Within a week or so they die.

At the season's end, a few adult house flies survive the winter's freeze in a warm corner of a building but most don't. Instead, most flies survive as maggots or pupae buried in manure or rotting grass. These start next year's swarms.

(Answered July 19, 2002)

Further Surfing:

Newton/Forest Preserve District of Cook County Illinois: The house fly