Female mosquitoes feed on human blood, not for their own nutritional purposes but in order to produce their eggs
The mosquito has a mouthpart called a proboscis, which is like a hypodermic needle.
She uses the proboscis to pierce your skin and probe around until she finds a capillary to suck the blood from
While biting, mosquitoes inject saliva into your body to stop your blood from coagulating; this is the point at which she can transmit diseases directly into your bloodstream.
How and Why Mosquitoes Bite
Female mosquitoes feed on human blood, but not for their own nutritional purposes. They need the protein and other components in the blood to produce their eggs.
The mosquito has a mouthpart called a proboscis, which is like a hypodermic needle. She uses it to pierce your skin and probe around a bit until she finds a capillary to suck the blood from.
She also injects some of her own saliva, which stops the blood from coagulating but is also the point at which she can transmit diseases directly into your bloodstream.2
She then sucks the blood out and into her abdomen, where it becomes digested and used to produce eggs. In the video below, you can see a close-up view of an Anopheles gambiae mosquito feeding on a capillary.