Since the common housefly only has a life cycle of 20-30 days, most of the time they won't even be around once the summer is over. A female housefly will typically lay 100-150 eggs at a time (and almost 500 over the course of her life!), which will turn into worm-like creatures called maggots a day later. Over the course of the next ten days, the maggots turn into pupae, which then hatch into adult flies, who meet up with new mates to start the cycle all over again. By the end of the summer, flies will have reproduced so many times that it would take humans almost 300 years to replicate those numbers!
However, flies do not do well in cold weather while one might get lucky and sneak into a house for a few days, most flies survive in maggot or pupae form until the weather is warm enough for them to starting hatching and mating again.
ExplorationSome animals tough out the winter months by finding a safe, warm place to stay, eating lots of food so their body can live off the extra fat, and sleeping until the winter is over! This is called "hibernating," and perhaps you've heard of some animals that do it “” can you name some? How about some species of frogs, snakes, bats, or even ladybugs!
Though they're commonly thought to be, bears are not considered "true" hibernators “” they may sleep for long periods of time during the colder months, but they will still get up for a short time to eat or walk around before going back to bed!
Sources & links
Cluster Flies." Iowa State University: Department of Entomology. 21 Sep. 2009. Fly." Encyclopædia Britannica. 2009. Encyclopædia Britannica Online. 21 Sep. 2009 House flies - here today, gone tomorrow." Wonder Quest. 21 Sep. 2009