Females use two different sources of food. They need sugar in nectar for energy and blood for protein which help to generate their eggs. Because biting is a dangerous work and the hosts are quite hard to find, mosquitoes feed on blood as much as possible. However, this cause other problem. In order to digest these blood, time is necessary and adult females need the energy in sugar while they are waiting.
To solve this problem, adult mosquitoes have a digestive system which may contain both of food and allow them using if necessary. When the mosquitoes suck sugar solution, they are moved to crop. Crop can lead sugar to stomach. In the same time, the stomachs are never full of sugar solution which prevent mosquitoes from feeding blood if they have chances.
Bloods are led directly into mosquito stomachs. In some bloodsuckers or birds – high blood pressure hosts, the adult female feed on blood collectively from active vascular where blood pressure will help to fill the stomachs quickly. Instead of killing a feeding mosquito, human can stretch their skin to grip the nozzle of mosquitoes and they cannot recover, the pressure will make their bowel distended and they will die. If they have no barrier, mosquito will pull their nozzle back and when their bowels are full, stomach substratum will create periodontal membrane around blood. This membrane has an ability to keep blood separated from other substances in stomach.
However, the same as other insect living by diluted and pure food, especially these insects belong to Hemiptera, many adult mosquitoes have to create unexpected water components even when feed on blood. If they are undetected, mosquitoes continue sucking blood until solid nutrition is enough. As the result, mosquitoes are full of blood and they continue absorbing sugar even though blood resolution process is slow in few days. When blood is in stomach, female midgut will synthetize enzyme and proteolysis to hydrolyze protein in blood into amino acid. It is used to synthetic protein.