Q. Where do flies sleep? I've encountered flies that were awake, but not one that was asleep (unless they're extremely light sleepers).

A. Flies become quiescent or "sleep" wherever they happen to be when the sun goes down. Frequently this is close to food sources or to substrates upon which they lay their eggs. Blowflies, for example, can be found very near or on carrion at night. You probably have not seen common flies sleeping because you do not frequent such locations yourself, particularly at night.

Robert Kimsey is a UC Davis assistant adjunct professor in the Department of Entomology.

Previous Ask it! questions:

Q. What is the biological or chemical explanation for that feeling I get when I hear a favorite song or see a moving performance, and I get tingles, or goose bumps, on the back of my neck and arms? 

Q. With so many birds in the world, and in our urban environment, you would think we would see dead birds all over the place. But we don't. So, where do birds go to die?

Q: Weight loss is based on expending more energy than consumed, and for every 3,000 calorie deficit you lose one pound. Assuming both an obese person and someone slightly overweight eat proportionate calories and exercise at equal levels, why does the obese person lose a lot more weight in the same amount of time than the slightly overweight person?

Q. Iowa and New Hampshire aren't exactly representative of the nation as a whole and yet they have so much influence on the presidential nominating process. Why are these states first every time?

Q. Would taking steroids or human growth hormone for a brief time, to aid recovery from an injury, be worth it? As a 50-plus athlete I don't care about improved performance, I care about decreasing injury recovery time.