The metabolism of dietary carbohydrates (nectar) and proteins (blood) explains may aspects of the behavior of adult mosquitoes. The energy flow of the reserve carbohydrates (glycogen) and fat (triglycerides) was followed at rest, in flight, and at different temperatures. A main characteristic of female mosquitoes is the accumulation of large amounts of fat from sugar meals, and the use of these reserves for survival at rest, but not for vigorous flight activity. Whether dietary sugar will be stored as glycogen (that is available for flight) or as fat, is regulated by neurosecretory cells of the brain. While sugar is used entirely for energetic purposes, a large blood meal may also contribute some nutrients for glycogen and fat accumulation.